the Soviet Union more than two decades ago, the United States has been the world’s sole great power. It maintains a military that is one order of magnitude more powerful than any other; ^(1){ }^{1} defense spending close to half of global military expenditures; ^(2){ }^{2} a blue-water navy superior to all others combined; ^(3){ }^{3} a chance at a splendid nuclear first strike over its erstwhile foe, Russia; ^(4){ }^{4} a defense research and development budget that is 80 percent of the total defense expenditures of its most obvious future competitor, China; ^(5){ }^{5} and unmatched global power-projection capabilities. ^(6){ }^{6} The post-Cold War international system is thus unipolar. 自二十多年前苏联解体以来，美国一直是世界上唯一的大国。 ^(1){ }^{1} 美国拥有比任何其他国家都强大一个数量级的军队； ^(1){ }^{1} 国防开支接近全球军费开支的一半； ^(2){ }^{2} 蓝水海军优于所有其他国家的总和； ^(3){ }^{3} 有机会对其昔日敌人俄罗斯实施精彩的核一击； ^(4){ }^{4} 国防研发预算是其最明显的未来竞争对手中国国防支出总额的 80%； ^(5){ }^{5} 以及无与伦比的全球力量投射能力。 ^(6){ }^{6} 因此，冷战后的国际体系是单极的。
The end of the Cold War took most observers by surprise, with little thought having been given to the possibility of a unipolar world. ^(7){ }^{7} Since then, however, a sizable literature on the topic has begun to focus on two issues: the durability and peacefulness of unipolar systems. ^(8){ }^{8} 冷战的结束令大多数观察家大吃一惊，他们几乎没有考虑过单极世界的可能性。 ^(7){ }^{7} 然而，从那时起，关于这一主题的大量文献开始关注两个问题：单极体系的持久性与和平性。 ^(8){ }^{8}
Throughout the 1990s, the prevailing argument was that unipolarity was not durable. Charles Krauthammer, for instance, wrote of a "unipolar moment."9 Structural realists such as Kenneth Waltz argued that other great powers would soon emerge to challenge the United States and reestablish the systemic balance of power. ^(10){ }^{10} Believers in the transient nature of unipolarity expressed little or no interest in the notion of unipolar peacefulness. 在整个 20 世纪 90 年代，流行的观点是单极化并不持久。例如，查尔斯-克劳瑟默（Charles Krauthammer）写道，"单极时刻 "即将来临。9 肯尼斯-华尔兹（Kenneth Waltz）等结构现实主义者认为，其他大国很快就会出现，挑战美国并重建系统性力量平衡。 ^(10){ }^{10} 相信单极化具有短暂性的人对单极和平的概念几乎不感兴趣。
In 1999, however, William Wohlforth challenged the consensus that unipolarity would soon end. Indeed, in “The Stability of a Unipolar World,” he underscored its durability. ^(11){ }^{11} U.S. preponderance is so marked, he wrote, that "[f]or many decades, no state is likely to be in a position to take on the United States in any of the underlying elements of power."12 然而，1999 年，威廉-沃尔福思对 "单极化将很快结束 "的共识提出了质疑。事实上，他在《单极化世界的稳定性》一文中强调了单极化的持久性。 ^(11){ }^{11} 他写道，美国的优势如此明显，以至于 "几十年内，没有一个国家可能在任何基本权力要素上与美国抗衡 "12。
Wohlforth further argued that a durable unipolar world is also a peaceful world. In his view, "the existing distribution of capabilities generates incentives for cooperation."13 U.S. power preponderance not only ends hegemonic rivalry but gives the United States incentives to manage security globally, limiting competition among major powers. ^(14){ }^{14} This benevolent view of unipolarity, which Wohlforth developed further in World Out of Balance: International Relations and the Challenge of American Primacy with his coauthor, Stephen Brooks, emerged as one of the most influential perspectives in debates about current international politics, echoing Francis Fukuyama’s popular view of the “end of history” and the universalization of Western liberal democracy. ^(15){ }^{15} 沃尔福思还认为，一个持久的单极世界也是一个和平的世界。在他看来，"现有的能力分配产生了合作的动力"。13 美国的实力优势不仅结束了霸权竞争，而且使美国有动力管理全球安全，限制了大国之间的竞争。 ^(14){ }^{14} 沃尔夫斯在《失衡的世界》（World Out of Balance：沃尔福思与合著者斯蒂芬-布鲁克斯（Stephen Brooks）在《失去平衡的世界：国际关系与美国主导地位的挑战》（World Out of Balance: International Relations and the Challenge of American Primacy）一书中进一步阐述了这种仁慈的单极化观点。 ^(15){ }^{15}
The question of unipolar durability remains the subject of spirited debate. Many analysts, such as Robert Kagan, continue to argue that "American predominance is unlikely to fade any time soon."16 Others, however, believe that it is in serious decline. ^(17){ }^{17} Potential peer competitors, especially China, are on the 单极的持久性问题仍然是激烈辩论的主题。许多分析人士，如罗伯特-卡根（Robert Kagan），仍然认为 "美国的主导地位不可能很快消退 "16 。 ^(17){ }^{17} 潜在的同行竞争者，尤其是中国，正在崛起。
rise. ^(18){ }^{18} U.S. travails in Afghanistan and Iraq seem to confirm Paul Kennedy’s argument on the inevitability of imperial overstretch, ^(19){ }^{19} and some see the financial crisis that began in 2008 as the death knell of U.S. predominance. ^(20){ }^{20} Given all of these factors, Robert Pape argues that "the unipolar world is indeed coming to an end. ^(21){ }^{21} 崛起。 ^(18){ }^{18} 美国在阿富汗和伊拉克的苦难似乎证实了保罗-肯尼迪关于帝国过度扩张不可避免的论点， ^(19){ }^{19} 一些人认为始于2008年的金融危机敲响了美国主导地位的丧钟。 ^(20){ }^{20} 鉴于所有这些因素，罗伯特-帕普认为 "单极世界确实即将终结。 ^(21){ }^{21}
In contrast, the question of unipolar peacefulness has received virtually no attention. Although the past decade has witnessed a resurgence of security studies, with much scholarship on such conflict-generating issues as terrorism, preventive war, military occupation, insurgency, and nuclear proliferation, no one has systematically connected any of them to unipolarity. This silence is unjustified. The first two decades of the unipolar era have been anything but peaceful. U.S. forces have been deployed in four interstate wars: Kuwait in 1991, Kosovo in 1999, Afghanistan from 2001 to the present, and Iraq between 2003 and 2010. ^(22){ }^{22} In all, the United States has been at war for thirteen of the twenty-two years since the end of the Cold War. ^(23){ }^{23} Put another way, the first two decades of unipolarity, which make up less than 10 percent of U.S. history, account for more than 25 percent of the nation’s total time at war. ^(24){ }^{24} And yet, the theoretical consensus continues to be that unipolarity encourages peace. Why? To date, scholars do not have a theory of how unipolar systems operate. ^(25){ }^{25} The debate on whether, when, and how unipolarity will end (i.e., the debate on durability) has all but monopolized our attention. 相比之下，单极和平的问题几乎没有受到任何关注。尽管过去十年见证了安全研究的复苏，对恐怖主义、预防性战争、军事占领、叛乱和核扩散等引发冲突的问题进行了大量研究，但没有人系统地将这些问题与单极性联系起来。这种沉默是毫无道理的。单极时代的头二十年并不和平。美国在四场国家间战争中部署了军队：1991年的科威特战争、1999年的科索沃战争、2001年至今的阿富汗战争以及2003年至2010年的伊拉克战争。 ^(22){ }^{22} 自冷战结束以来的22年中，美国总共有13年处于战争状态。 ^(23){ }^{23} 换句话说，单极化的前二十年只占美国历史的不到10%，却占美国战争总时间的25%以上。 ^(24){ }^{24} 然而，理论界的共识仍然是单极化鼓励和平。为什么会这样呢？迄今为止，学者们还没有关于单极体系如何运作的理论。 ^(25){ }^{25} 关于单极化是否会结束、何时结束以及如何结束的争论（即关于持久性的争论）几乎垄断了我们的注意力。
In this article, I provide a theory of unipolarity that focuses on the issue of unipolar peacefulness rather than durability. I argue that unipolarity creates significant conflict-producing mechanisms that are likely to involve the unipole itself. Rather than assess the relative peacefulness of unipolarity vis-à-vis bipolar or multipolar systems, I identify causal pathways to war that are characteristic of a unipolar system and that have not been developed in the extant literature. To be sure, I do not question the impossibility of great power war in a unipolar world. Instead, I show how unipolar systems provide incentives for two other types of war: those pitting the sole great power against another state and those involving exclusively other states. In addition, I show that the type of conflict that occurs in a unipolar world depends on the strategy of the sole great power, of which there are three. The first two-defensive and offensive dominance-will lead to conflicts pitting the sole great power against other states. The third-disengagement-will lead to conflicts among other states. Furthermore, whereas the unipole is likely to enter unipolarity implementing a dominance strategy, over time it is possible that it will shift to disengagement. 在这篇文章中，我提出了一种单极性理论，其重点在于单极的和平性而非持久性问题。我认为，单极性产生了重要的冲突制造机制，而这些机制很可能涉及单极本身。我没有评估单极相对于两极或多极体系的相对和平性，而是指出了单极体系特有的、现有文献中尚未论及的战争因果途径。当然，我并不质疑单极世界不可能发生大国战争。相反，我说明了单极体系如何为其他两种类型的战争提供了诱因：一种是唯一的大国与另一个国家的战争，另一种是只涉及其他国家的战争。此外，我还展示了单极世界中发生的冲突类型取决于唯一大国的战略，其中有三种。前两种战略--防御性和进攻性主导--将导致唯一大国与其他国家的冲突。第三种--脱离接触--将导致其他国家之间的冲突。此外，虽然单极大国在进入单极时代时可能会实施主导战略，但随着时间的推移，它有可能会转向脱离接触。
I support my theory with several empirical examples. These do not aim at systematically testing my argument, for two reasons. First, the unipolar era is too short a period to test structural mechanisms. Second, the United States has consistently implemented a strategy of dominance, limiting opportunities to test my claims on the consequences of disengagement. ^(26){ }^{26} 我用几个经验实例来支持我的理论。这些例子并不是为了系统地检验我的论点，原因有二。首先，单极时代的时间太短，无法检验结构性机制。其次，美国一直在实施主导战略，这限制了检验我关于脱离接触后果的主张的机会。 ^(26){ }^{26}
The remainder of this article proceeds as follows. In the first section, I define the key terms used in my theory. In the second section, I review the literature on unipolarity and peace. In the third section, I lay out my theory. The next three sections discuss the three strategies of defensive dominance, offensive dominance, and disengagement and show how each can produce conflict. In the conclusion, I discuss implications for theory and policy. 本文接下来的内容如下。在第一部分，我定义了我的理论中使用的关键术语。第二部分，我回顾了有关单极化与和平的文献。在第三部分，我阐述了我的理论。接下来的三节讨论了防御性主导、进攻性主导和脱离接触这三种战略，并说明了每种战略如何产生冲突。在结论部分，我将讨论对理论和政策的影响。
Key Concepts 关键概念
In this section, I define unipolarity, distinguish it from other systems, describe the types of state that exist in a unipolar world, and introduce a typology of possible wars among them. ^(27){ }^{27} 在本节中，我将定义单极化，将其与其他体系区分开来，描述单极世界中存在的国家类型，并介绍它们之间可能发生的战争类型。 ^(27){ }^{27}
Unipolar systems have three defining features. First, unipolarity is an interstate system. Thus, it is not coeval with empire. ^(28){ }^{28} As Robert Jervis notes, “Unipolarity implies the existence of many juridically equal nation-states, something an empire denies.” ^('29){ }^{\prime 29} As Daniel Nexon and Thomas Wright explain, in empires, intersocietal divide-and-rule practices replace interstate balance-of-power dynamics. ^(30){ }^{30} These differences are significant enough that my theory, which focuses on balance of power dynamics, should not be expected to account for imperial systems. 单极体系有三个显著特点。首先，单极化是一种国家间体系。因此，它与帝国不是共生的。 ^(28){ }^{28} 正如罗伯特-杰维斯指出的，"单极性意味着存在许多在法律上平等的民族国家，这是帝国所否认的"。 ^('29){ }^{\prime 29} 正如丹尼尔-尼克松和托马斯-赖特所解释的那样，在帝国中，社会间的分而治之取代了国家间的均势。 ^(30){ }^{30} 这些差异非常明显，因此，我的理论侧重于均势动态，不应指望它能解释帝国体系。
Second, unipolarity is anarchical. Anarchy results from the incomplete power preponderance of the unipole. As Waltz puts it, a great power cannot “exert a positive control everywhere in the world.” ^(31){ }^{31} Other states have significant freedom of action and may well pursue independent policy preferences on issues they care more about than the unipole. ^(32){ }^{32} By highlighting the limits of the unipole’s power, anarchy helps to distinguish between unipolar and hegemonic systems. ^(33){ }^{33} If the unipole increases its power to the point where it can control the external behavior of all other states, then it has become a hegemon, making the system hierarchical. My theory would no longer apply. 其次，单极化是无政府的。无政府状态源于单极不完全的力量优势。正如华尔兹所说，大国不可能 "在世界任何地方都实施积极的控制"。 ^(31){ }^{31} 其他国家有很大的行动自由，在它们比单极更关心的问题上，它们很可能会追求独立的政策偏好。 ^(32){ }^{32} 通过强调单极力量的局限性，无政府状态有助于区分单极体系和霸权体系。 ^(33){ }^{33} 如果单极国家的力量增强到可以控制所有其他国家的外部行为，那么它就成为了霸权国家，从而使整个体系等级分明。我的理论就不再适用了。
Third, unipolar systems possess only one great power, which enjoys a preponderance of power and faces no competition. ^(34){ }^{34} (As soon as competition emerges, the system is no longer unipolar.) Unlike in bipolar and multipolar systems, there is no systemic balance of power in a unipolar system. Today, Waltz would say that the United States is the only “pole” to possess "global interests which it can care for unaided, though help may often be desirable."35 第三，单极体系只拥有一个大国，它享有绝对优势，不面临任何竞争。<与两极和多极体系不同，单极体系中不存在系统性的力量平衡。今天，华尔兹会说，美国是拥有 "全球利益的唯一'一极'，它可以在没有帮助的情况下照顾这些利益，尽管帮助可能经常是可取的 "35。
By distinguishing unipolarity from hegemonic, imperial, bipolar, and multi- 将单极与霸权、帝国、两极和多极区分开来。
polar systems, my definition reveals the unique historical character of the post-Cold War era. History records numerous empires, including ancient Egypt, Persia, China, and Rome. France under Louis XIV and again under Napoleon I, and the United States in 1945-49 are cases of bipolar or (unbalanced) multipolar systems, in which at least two states have commensurate power-projection capabilities, though of different types. Napoleonic France, though a potential continental hegemon in Europe, was no match for British naval power. Similarly, early-Cold War U.S. power was balanced by that of the Soviet Union, which possessed unquestioned conventional superiority on the Eurasian landmass. In short, since the end of the Cold War, an unprecedented unipolar United States has operated in an anarchic interstate system. 我的定义揭示了后冷战时代的独特历史特征。历史上有无数帝国，包括古埃及、波斯、中国和罗马。路易十四时期的法国和拿破仑一世时期的法国，以及 1945-49 年的美国，都是两极或（不平衡的）多极体系的案例，在这些体系中，至少有两个国家拥有相称的力量投射能力，尽管类型不同。拿破仑时期的法国虽然是欧洲大陆的潜在霸主，但其海军力量却不是英国的对手。同样，冷战初期美国的力量也被苏联所制衡，后者在欧亚大陆拥有无可置疑的常规优势。总之，自冷战结束以来，一个前所未有的单极美国在一个无政府的国家间体系中运作。
To say that the world is unipolar is to describe the systemic distribution of power, not the strategy of the sole great power. A unipole can pursue one of three grand strategies: defensive dominance, offensive dominance, or disengagement. ^(36){ }^{36} The key to distinguishing among them is the unipole’s attitude toward the global status quo, which I define based on three components: territorial arrangements, international political alignments, and the global distribution of power. Using an offensive-dominance strategy, the unipole seeks to revise at least one of the status quo’s components in its favor. With a strategy of defensive dominance, it tries to maintain all three components. In a strategy of disengagement, it pays no attention to the maintenance of the international status quo, allowing others to change it in their favor. 说世界是单极的，是描述权力的系统分布，而不是唯一大国的战略。单极大国可以奉行三种大战略之一：防御性主导、进攻性主导或脱离接触。 ^(36){ }^{36} 区分这三种大战略的关键在于单极对全球现状的态度，我是根据领土安排、国际政治结盟和全球权力分配这三个要素来定义全球现状的。通过进攻主导战略，单极试图改变现状的至少一个组成部分，使其对自己有利。在防御主导战略中，它试图维持所有三个组成部分。在脱离战略中，单极不重视维持国际现状，而是让其他国家改变现状，使之有利于自己。
In a unipolar system, states other than the sole great power can be divided into two categories. The first category comprises major powers, which, even though their power-projection capabilities are inferior to those of the unipole, possess sufficient capabilities to deter any state in the system. (To do this, a 在单极体系中，除了唯一的大国之外，其他国家可分为两类。第一类是大国，尽管它们的力量投射能力不如单极，但有足够的能力威慑体系中的任何国家。(要做到这一点，一个
country must have a plausible chance of avoiding defeat in an all-out defensive war against a potential aggressor.) Examples from this category include all of the nuclear powers beyond the United States: China, France, India, Israel, North Korea, Pakistan, Russia, and the United Kingdom. The second category is composed of states that lack sufficient capabilities to deter the unipole, or socalled minor powers. ^(37){ }^{37} 国家必须有合理的机会避免在与潜在侵略者的全面防御战中战败）。这类国家包括美国之外的所有核大国：中国、法国、印度、以色列、朝鲜、巴基斯坦、俄罗斯和英国。第二类是缺乏足够能力威慑单极的国家，即所谓的小国。 ^(37){ }^{37}
Unipolarity thus yields a typology of states that captures two fundamental differences: between the unipole and all other states, which lack comparable power-projection capabilities; and between major powers, which can deter the unipole, and minor powers, which cannot. From this typology, I derive six kinds of war according to the rank of the belligerents: wars between (1) great powers, (2) a great power and a major power, (3) a great power and a minor power, (4) two major powers, (5) a major power and a minor power, and (6) two minor powers. In the next section, I discuss the conventional argument that unipolarity is peaceful and describe its predictions for each of these types of war. 因此，单极性产生了一种国家类型学，它抓住了两个根本区别：一是单极国家与所有其他国家之间的区别，后者缺乏可比的力量投射能力；二是大国与小国之间的区别，前者能够威慑单极国家，后者则不能。从这一类型学出发，我根据交战国的等级推导出六种战争：(1) 大国之间的战争；(2) 一个大国和一个大国之间的战争；(3) 一个大国和一个小国之间的战争；(4) 两个大国之间的战争；(5) 一个大国和一个小国之间的战争；(6) 两个小国之间的战争。在下一节中，我将讨论单极化是和平的这一传统论点，并描述其对每种战争类型的预测。
Unipolarity and Peace 单极化与和平
Wohlforth offers a concise argument that unipolarity is peaceful: 沃尔福思简明扼要地论证了单极化是和平的：
[T]he current unipolarity is prone to peace. The raw power advantage of the United States means that an important source of conflict in previous systems is absent: hegemonic rivalry over leadership of the international system. No other major power is in a position to follow any policy that depends for its success on prevailing against the United States in a war or an extended rivalry. None is likely to take any step that might invite the focused enmity of the United States. At the same time, unipolarity minimizes security competition among the other great powers. As the system leader, the United States has the means and motive to maintain key security institutions in order to ease local security conflicts and limit expensive competition among the other major powers. For their part, the second-tier states face incentives to bandwagon with the unipolar power as long as the expected costs of balancing remain prohibitive. ^(38){ }^{38} [当前的单极化容易带来和平。美国的原始力量优势意味着，以往体系中的一个重要冲突根源不复存在：对国际体系领导权的霸权争夺。任何其他大国都不会采取任何取决于在战争或长期竞争中战胜美国的政策。任何国家都不可能采取任何可能招致美国重点敌视的措施。同时，单极化将其他大国之间的安全竞争降至最低。作为体系领导者，美国有能力也有动机维持关键的安全机构，以缓和地方安全冲突，限制其他大国之间代价高昂的竞争。而二线国家则面临着与单极大国结盟的动机，只要平衡的预期成本仍然过高。 ^(38){ }^{38}
Wohlforth claims not only that the unipole can stave off challenges and preclude major power rivalries, but also that it is able to prevent conflicts among other states and create incentives for them to side with it. ^(39){ }^{39} The unipole’s advantage is so great that it can settle any quarrel in which it intervenes. As Wohlforth writes, "For as long as unipolarity obtains, . . . second-tier states are less likely to engage in conflict-prone rivalries for security or prestige. Once the sole pole takes sides, there can be little doubt about which party will prevail. ^('40){ }^{\prime 40} This is the core logic of Wohlforth’s argument that unipolarity is peaceful. But what specifically does his argument say about each of the six possible kinds of war I identified in the previous section? 沃尔福思称，单极不仅可以避免挑战，排除大国竞争，还能防止其他国家之间的冲突，并鼓励它们站在自己一边。 ^(39){ }^{39} 单极的优势如此之大，以至于它可以解决它介入的任何争吵。沃尔福思写道："只要单极存在，......二线国家就不太可能为了安全或声望而参与容易引发冲突的竞争。一旦唯一的一极选边站队，哪一方将获胜就几乎没有疑问了。 ^('40){ }^{\prime 40} 这就是沃尔夫特关于单极化是和平的论点的核心逻辑。但是，对于我在上一节中指出的六种可能的战争，他的论点又是如何具体阐述的呢？
Clearly, great power war is impossible in a unipolar world. In Wohlforth’s famous formulation: "Two states measured up in 1990. One is gone. No new pole has appeared: 2-1=1.^(111)2-1=1 .{ }^{111} Furthermore, by arguing that unipolarity precludes hegemonic rivalries, Wohlforth makes no room for wars between the sole great power and major powers. These are, according to him, the two main reasons why a unipolar world is peaceful. Unipolarity, he writes, “means the absence of two big problems that bedeviled the statesmen of past epochs: hegemonic rivalry and balance-of-power politics among major powers.” ^(42){ }^{42} 显然，单极世界不可能发生大国战争。用沃尔福斯的著名表述来说，就是"1990年有两个国家。一个已经消失。没有出现新的极点： 2-1=1.^(111)2-1=1 .{ }^{111} 此外，由于认为单极性排除了霸权竞争，沃尔福思也就没有了唯一大国与大国之间战争的空间。他认为，这是单极世界之所以和平的两个主要原因。他写道，单极化 "意味着不存在困扰过去时代政治家的两大问题：霸权竞争和大国间的均势政治"。 ^(42){ }^{42}
I agree with Wohlforth on these two points, but they are only part of the picture. Granted, the absence of great power wars is an important contribution toward peace, but great power competition-and the conflict it might engender-would signal the emergence of one or more peer competitors to the unipole, and thus indicate that a transition to a bipolar or multipolar system was already under way. In this sense, great power conflict should be discussed 在这两点上，我同意沃尔福思的观点，但它们只是问题的一部分。诚然，没有大国战争是对和平的重要贡献，但大国竞争--及其可能引发的冲突--将预示着出现了一个或多个单极的同行竞争者，从而表明向两极或多极体系的过渡已经开始。从这个意义上说，应该讨论大国冲突
within the context of unipolar durability, not unipolar peace. Indeed, including this subject in discussions of unipolar peacefulness parallels the mistakes made in the debate about the Cold War bipolar system. Then, arguments about how the two superpowers were unlikely to fight each other were often taken to mean that the system was peaceful. This thinking ignored the possibility of wars between a superpower and a lesser state, as well as armed conflicts among two or more lesser states, often acting as great power proxies. ^(43){ }^{43} 在单极持久性的背景下，而不是在单极和平的背景下。事实上，在讨论单极和平问题时加入这一话题，与冷战时期两极体系辩论中所犯的错误如出一辙。当时，关于两个超级大国不太可能互相争斗的论点往往被认为意味着该体系是和平的。这种想法忽视了超级大国与较小国家之间发生战争的可能性，也忽视了两个或更多较小国家之间的武装冲突，而这些国家往往是大国的代理人。 ^(43){ }^{43}
In addition, Wohlforth claims that wars among major powers are unlikely, because the unipole will prevent conflict from erupting among important states. He writes, "The sole pole’s power advantages matter only to the degree that it is engaged, and it is most likely to be engaged in politics among the other major powers. ^(44){ }^{44} I agree that if the unipole were to pursue a strategy of defensive dominance, major power wars would be unlikely. Yet, there is no compelling reason to expect that it will always follow such a course. Should the unipole decide to disengage, as Wohlforth implies, major power wars would be possible. 此外，沃尔福思还声称，大国之间不太可能发生战争，因为单极会阻止重要国家之间爆发冲突。他写道："唯一极点的权力优势只有在它参与的程度上才是重要的，而它最有可能参与其他大国之间的政治。 ^(44){ }^{44} 我同意，如果单极奉行防御性主导战略，大国战争就不太可能发生。然而，我们并没有令人信服的理由来期待它将始终奉行这一路线。如果单极决定脱离，正如沃尔福思所暗示的那样，大国战争就有可能发生。
At the same time, Wohlforth argues that the unipole’s power preponderance makes the expected costs of balancing prohibitive, leading minor powers to bandwagon. This is his explanation for the absence of wars between the sole great power and minor powers. But, as I show, the costs of balancing relative to bandwagoning vary among minor powers. So Wohlforth’s argument underplays the likelihood of this type of war. 同时，沃尔福思认为，单极大国的力量优势使得平衡的预期成本过高，导致小国拉帮结派。这就是他对唯一大国与小国之间没有战争的解释。但是，正如我所展示的，相对于拉帮结派，小国之间的平衡成本是不同的。因此，沃尔福思的论点低估了这类战争的可能性。
Finally, Wohlforth’s argument does not exclude all kinds of war. Although power preponderance allows the unipole to manage conflicts globally, this argument is not meant to apply to relations between major and minor powers, or among the latter. As Wohlforth explains, his argument “applies with less force to potential security competition between regional powers, or between a second-tier state and a lesser power with which the system leader lacks close ties.” ^(15){ }^{15} Despite this caveat, Wohlforth does not fully explore the consequences of potential conflict between major and minor powers or among the latter for his view that unipolarity leads to peace. 最后，沃尔福思的论点并不排除所有类型的战争。虽然权力优势使单极能够管理全球冲突，但这一论点并不适用于大国与小国之间的关系，也不适用于后者之间的关系。正如沃尔福思所解释的那样，他的论点 "适用于地区大国之间的潜在安全竞争，或二线国家与系统领导者缺乏密切关系的小国之间的潜在安全竞争，但力度较小"。 ^(15){ }^{15} 尽管提出了这一注意事项，但沃尔福斯并没有充分探讨大国与小国之间或小国与大国之间的潜在冲突对他的单极化导致和平这一观点的影响。
How well, then, does the argument that unipolar systems are peaceful account for the first two decades of unipolarity since the end of the Cold War? Table 1 presents a list of great powers divided into three periods: 1816 to 1945, 那么，"单极体系是和平的 "这一论点能否很好地解释冷战结束后前二十年的单极化呢？表 1 列出了分为三个时期的大国名单：1816 年至 1945 年、
Multipolarity Bipolarity Unipolarity
Dates Years Dates Years Dates Years
Austro-Hungarian Empire 1816-1918 103
France 1816-1940 125
Prussia/Germany "1816-1918//
1925-45" 124
Italy 1860-1943 84
Japan 1895-1945 51
United Kingdom 1816-1945 130
Russia / Soviet Union "1816-1917//
1922-45" 126 1946-89 44
United States 1898-1945 48 1946-89 44 1990-2011 22
Total 791 88 22| | Multipolarity | | Bipolarity | | Unipolarity | |
| :---: | :---: | :---: | :---: | :---: | :---: | :---: |
| | Dates | Years | Dates | Years | Dates | Years |
| Austro-Hungarian Empire | 1816-1918 | 103 | | | | |
| France | 1816-1940 | 125 | | | | |
| Prussia/Germany | $\begin{gathered} 1816-1918 / \\ 1925-45 \end{gathered}$ | 124 | | | | |
| Italy | 1860-1943 | 84 | | | | |
| Japan | 1895-1945 | 51 | | | | |
| United Kingdom | 1816-1945 | 130 | | | | |
| Russia / Soviet Union | $\begin{gathered} 1816-1917 / ~ \\ 1922-45 \end{gathered}$ | 126 | 1946-89 | 44 | | |
| United States | 1898-1945 | 48 | 1946-89 | 44 | 1990-2011 | 22 |
| Total | | 791 | | 88 | | 22 |
SOURCES: Data are from the Correlates of War, ver. 4.0, dataset, modified by the author as follows: only the Soviet Union and the United States are counted as great powers from 1946 to 1989, and only the United States is counted as a great power since 1990. See Reid Sarkees and Frank Wayma, Resort to War: A Data Guide to Inter-state, Extra-state, Intrastate, and Non-state Wars, 1816-2007 (Washington, D.C.: CO Press, 2010). 资料来源数据来自 Correlates of War, ver.4.0 版，数据集，经作者修改如下：1946 年至 1989 年，只有苏联和美国被算作大国，1990 年以来，只有美国被算作大国。见 Reid Sarkees 和 Frank Wayma，《诉诸战争：国家间、国家外、国家内和非国家战争数据指南，1816-2007 年》（华盛顿特区：CO Press，2010 年）。
Table 2. Interstate Wars Involving Great Powers since 1816 表 2.1816 年以来涉及大国的国家间战争
Multipolarity 多极化
Bipolarity 双极性
Unipolarity 单极性
Great power years 伟大的权力岁月
791
88
22
Great power years at war 战争年代的大国
143
14
13
Percentage of great power years at war 大国战争年所占百分比
18%18 \%
16%16 \%
59%59 \%
Wars involving great powers 大国战争
33
3
4
Incidence of war per great power year 每个大国年的战争发生率
4.2%4.2 \%
3.4%3.4 \%
18.2%18.2 \%
Multipolarity Bipolarity Unipolarity
Great power years 791 88 22
Great power years at war 143 14 13
Percentage of great power years at war 18% 16% 59%
Wars involving great powers 33 3 4
Incidence of war per great power year 4.2% 3.4% 18.2%| | Multipolarity | Bipolarity | Unipolarity |
| :--- | :--- | :--- | :--- |
| Great power years | 791 | 88 | 22 |
| Great power years at war | 143 | 14 | 13 |
| Percentage of great power years at war | $18 \%$ | $16 \%$ | $59 \%$ |
| Wars involving great powers | 33 | 3 | 4 |
| Incidence of war per great power year | $4.2 \%$ | $3.4 \%$ | $18.2 \%$ |
SOURCES: Data are from the Correlates of War, ver. 4.0, dataset. See Reid Sarkees and Frank 资料来源数据来自 Correlates of War, ver.4.0 数据集。见 Reid Sarkees 和 Frank
Wayma, Resort to War: A Data Guide to Inter-state, Extra-state, Intra-state, and Non-state Wars, 1816-2007 (Washington, D.C.: CO Press, 2010). Wayma, Resort to War: A Data Guide to Inter-state, Extra-state, Intra-state, and Non-state Wars, 1816-2007 (Washington, D.C.: CO Press, 2010)。
multipolarity; 1946 to 1989, bipolarity; and since 1990, unipolarity. ^(46){ }^{46} Table 2 presents summary data about the incidence of war during each of these periods. Unipolarity is the most conflict prone of all the systems, according to at least two important criteria: the percentage of years that great powers spend at war and the incidence of war involving great powers. In multipolarity, 18 percent of great power years were spent at war. In bipolarity, the ratio is 16 percent. In unipolarity, however, a remarkable 59 percent of great power 多极化；1946 年至 1989 年为两极化；1990 年以来为单极化。 ^(46){ }^{46} 表 2 列出了每个时期战争发生率的简要数据。从至少两个重要标准来看，单极化是所有体系中最容易发生冲突的：大国发生战争的年数百分比和大国卷入战争的发生率。在多极化体系中，18%的大国战争年。在两极格局中，这一比例为 16%。然而，在单极化中，有 59% 的大国在战争中丧生。
years until now were spent at war. This is by far the highest percentage in all three systems. Furthermore, during periods of multipolarity and bipolarity, the probability that war involving a great power would break out in any given year was, respectively, 4.2 percent and 3.4 percent. Under unipolarity, it is 18.2 percent-or more than four times higher. ^(47){ }^{47} These figures provide no evidence that unipolarity is peaceful. ^(48){ }^{48} 年是在战争中度过的。这是迄今为止三种体系中最高的比例。此外，在多极化和两极化时期，任何一年爆发大国战争的概率分别为 4.2% 和 3.4%。而在单极化时期，这一概率为 18.2%，高出四倍多。 ^(47){ }^{47} 这些数字无法证明单极化是和平的。 ^(48){ }^{48}
In sum, the argument that unipolarity makes for peace is heavily weighted toward interactions among the most powerful states in the system. This should come as no surprise given that Wohlforth makes a structural argument: peace flows from the unipolar structure of international politics, not from any particular characteristic of the unipole. ^(49){ }^{49} Structural analyses of the international system are usually centered on interactions between great powers. ^(50){ }^{50} As Waltz writes, “The theory, like the story, of international politics is written in terms of the great powers of an era.” ^(51){ }^{51} In the sections that follow, however, 总之，单极性造就和平的论点主要倾向于体系中最强大国家之间的互动。鉴于沃尔福思提出的是结构性论点：和平源于国际政治的单极结构，而非单极的任何特定特征，这一点不足为奇。 ^(49){ }^{49} 国际体系的结构性分析通常以大国之间的互动为中心。 ^(50){ }^{50} 正如华尔兹写道："国际政治的理论，就像故事一样，是以一个时代的大国来书写的"。 ^(51){ }^{51} 然而，在接下来的章节中、
47. This sharp increase in both the percentage of great power years spent at war and the incidence of conflict is particularly puzzling given that the current unipole-the United States-is a democracy in a world populated by more democracies than ever before. In light of arguments about how democracies are (1) better able to solve disputes peacefully, (2) select only into those wars they can win, and (3) tend to fight shorter wars, this should mean that the United States would spend fewer years at war than previous nondemocratic great powers. On democracies’ bargaining advantages, see Bruce Bueno de Mesquita, Alastair Smith, Randolph M. Siverson, and James D. Morrow, The Logic of Political Survival (Cambridge, Mass.: MIT Press, 2003); and Darren Filson and Suzanne Werner, “Bargaining and Fighting: The Impact of Regime Type on War Onset, Duration, and Outcomes,” American Journal of Political Science, Vol. 48, No. 2 (Fall 2004), pp. 296-313. On selection effects, see Dan Reiter and Allan C. Stam, Democracies at War (Princeton, N.J.: Princeton University Press, 2002). On democracies fighting shorter wars, see D. Scott Bennett and Allan C. Stam, “The Declining Advantages of Democracy: A Combined Model of War Outcomes and Duration,” Journal of Conflict Resolution, Vol. 42, No. 3 (June 1998), pp. 344-366. 47.鉴于当前的单极国家--美国--是一个民主国家，而世界上的民主国家比以往任何时候都多，因此大国战争年限和冲突发生率的大幅增长尤其令人费解。鉴于有关民主国家如何（1）更能和平解决争端，（2）只选择那些他们能打赢的战争，以及（3）倾向于打更短的战争的论点，这应该意味着美国的战争年限会比以前的非民主大国要少。关于民主国家的讨价还价优势，见布鲁斯-布埃诺-德-梅斯基塔（Bruce Bueno de Mesquita）、阿拉斯泰尔-史密斯（Alastair Smith）、伦道夫-M-西弗森（Randolph M. Siverson）和詹姆斯-D-莫罗（James D. Morrow），《政治生存的逻辑》（The Logic of Political Survival）（马萨诸塞州剑桥：麻省理工学院出版社，2003 年）；以及达伦-费尔森（Darren Filson）和苏珊娜-维尔纳（Suzanne Werner），《讨价还价与战斗》（Bargaining and Fighting：The Impact of Regime Type on War Onset, Duration, and Outcomes," American Journal of Political Science, Vol. 48, No.关于选择效应，见 Dan Reiter 和 Allan C. Stam，Democracies at War（新泽西州普林斯顿：普林斯顿大学出版社，2002 年）。关于民主国家的战争时间较短，见 D. Scott Bennett 和 Allan C. Stam, "The Declining Advantages of Democracy：A Combined Model of War Outcomes and Duration," Journal of Conflict Resolution, Vol. 42, No.
48. Some scholars might argue that wars in the post-Cold War world have been less lethal than those of the past. See, for example, Bethany Encina and Nils Petter Gleditch, “Monitoring Trends in Global Combat: A New Dataset of Battle Deaths,” European Journal of Population, Vol. 21, Nos. 2 / 3 (June 2005), pp. 145-166. It is difficult, however, to parse the role of polarity in a decrease in lethality. See Bruce Russett, “Peace in the Twenty-First Century?” Current History, January 2010, p. 11. Furthermore, part of the explanation for this decrease in lethality may lie in the U.S. decision to develop a highly capitalized military aimed at minimizing casualties. See Jonathan D. Caverley, “Death and Taxes: Sources of Democratic Military Aggression,” Ph.D. dissertation, University of Chicago, 2008; and Jason Lyall and Isaiah Wilson III, “Rage against the Machines: Explaining Outcomes in Counterinsurgency Wars,” International Organization, Vol. 63, No. 1 (Winter 2009), pp. 67106. 48.一些学者可能会说，冷战后世界的战争比过去的战争更不致命。例如，见 Bethany Encina 和 Nils Petter Gleditch，"Monitoring Trends in Global Combat：A New Dataset of Battle Deaths," European Journal of Population, Vol. 21, Nos.然而，要分析极性在致命性下降中的作用并不容易。见 Bruce Russett，"21 世纪的和平？当前历史》，2010 年 1 月，第 11 页。此外，致命性下降的部分原因可能在于美国决定发展一支高度资本化的军队，以尽量减少伤亡。见 Jonathan D. Caverley, "Death and Taxes：Sources of Democratic Military Aggression," Ph.D. dissertation, University of Chicago, 2008; and Jason Lyall and Isaiah Wilson III, "Rage against the Machines：解释反叛乱战争的结果》，《国际组织》，第 63 卷，第 1 期（2009 年冬），第 67106 页。
49. See Wohlforth, “The Stability of a Unipolar World,” p. 8 n. 12. 49.见 Wohlforth，"单极世界的稳定性"，第 8 页 n. 12。
50. See Michael Mastanduno, “Preserving the Unipolar Moment: Realist Theories and U.S. Grand Strategy after the Cold War,” International Security, Vol. 21, No. 4 (Spring 1997), p. 50. 50.见 Michael Mastanduno, "Preserving the Unipolar Moment：现实主义理论与冷战后的美国大战略》，《国际安全》，第 21 卷，第 4 期（1997 年春），第 50 页。
51. Waltz, Theory of International Politics, p. 72. By setting “the smallest possible number [of great powers] in a self-help system” at two, however, Waltz has nothing to say on the workings of a unipolar system. See ibid., p. 136. Taking him at his word, Brooks and Wohlforth question the applicability of structural balance of power theory to a unipolar world. See Brooks and Wohlforth, World Out of Balance, p. 48. My argument shows how, much to the contrary, applying balance of power theory to a unipolar world provides important analytical insight. Waltz seems to have recently acknowledged this. When asked in an interview what would he change if he were to write Theory of 51.华尔兹，《国际政治理论》，第 72 页。然而，华尔兹将 "自助体系中[大国]的最小可能数量 "设定为两个，这就使得他对单极体系的运作一无所知。见同上，第 136 页。布鲁克斯（Brooks）和沃尔夫斯（Wohlforth）信以为真，质疑结构性均势理论对单极世界的适用性。见 Brooks and Wohlforth, World Out of Balance, 第 48 页。我的论点表明，恰恰相反，将均势理论应用于单极世界可以提供重要的分析见解。华尔兹最近似乎承认了这一点。在一次采访中，当被问及如果他再写《世界失衡论》，会对哪些地方做出改动时，华尔兹说
I show that in the case of unipolarity, an investigation of its peacefulness must consider potential causes of conflict beyond interactions between the most important states in the system. 我表明，在单极性的情况下，对其和平性的研究必须考虑到冲突的潜在原因，而不仅仅是体系中最重要国家之间的互动。
Unipolarity, Strategy, and Conflict 单极化、战略与冲突
In this section, I analyze how the unipole’s strategic choices-defensive dominance, offensive dominance, or disengagement-can trigger conflictproducing mechanisms between the unipole and other states, or among the latter. I take the distribution of power between the unipole and major powers as fixed. The ways in which unipolarity may be transformed into either a bipolar or a multipolar order, which may or may not lead to conflict, are beyond the scope of my argument. So are the ways in which the unipole may increase its power preponderance and become a global hegemon or an empire. Thus, my theory lays out how each of the unipole’s grand strategic choices produces conflict in the context of a unipolar structure that is at least somewhat durable. 在本节中，我将分析单极国家的战略选择--防御性主导、进攻性主导或脱离接触--如何在单极国家与其他国家之间或后者之间引发冲突的机制。我认为单极与大国之间的权力分配是固定的。至于单极如何转变为两极或多极秩序，从而导致或不导致冲突，不在我的论述范围之内。单极如何增强其实力优势，成为全球霸主或帝国，也不在我的论述范围之内。因此，我的理论阐述了在单极结构至少具有一定持久性的背景下，单极的每一种大战略选择是如何产生冲突的。
Specifically, I show how, in addition to wars between major and minor powers and to wars among the latter, two other types of war are likely to be prevalent in a unipolar world. First, and resulting from either of the dominance strategies, are wars pitting the sole great power against minor powers. Second, and stemming from a disengagement strategy, are major power wars. My theory explores the different mechanisms leading to each type of war. 具体而言，我将说明，除了大国与小国之间的战争以及小国之间的战争之外，在单极世界中还可能发生另外两种类型的战争。首先，由任何一种主导战略引发的战争都是唯一的大国与小国之间的战争。其次，由脱离战略引发的是大国战争。我的理论探讨了导致每种类型战争的不同机制。
My theory therefore differs from Wohlforth’s in two key aspects. First, Wohlforth believes that power preponderance in a unipolar system is so marked that the expected costs of balancing are always prohibitive. Consequently, every state in the system will bandwagon with the unipole, making it impossible for the latter to be involved in wars. In contrast, I show that some states face lower costs of balancing relative to bandwagoning. They are therefore more likely to become recalcitrant minor powers, with whom the sole great power is likely to go to war even when implementing a defensivedominance strategy. 因此，我的理论在两个关键方面不同于沃尔福思的理论。首先，沃尔福思认为，在单极体系中，力量优势是如此明显，以至于平衡的预期成本总是过高。因此，体系中的每个国家都会与单极国家结盟，使后者无法卷入战争。与此相反，我的研究表明，相对于拉帮结派，一些国家面临的平衡成本更低。因此，这些国家更有可能成为顽固的小国，即使实施防御主导战略，唯一的大国也有可能与之开战。
Second, Wohlforth assumes that the unipole will always implement a strategy of defensive dominance: it will not engage in offensive revisionism, nor will it disengage from the world. I show how both offensive dominance and 其次，沃尔福思假定单极将始终实施防御性主导战略：它不会参与进攻性修正主义，也不会脱离世界。我将展示进攻性主导和
disengagement are plausible strategic options for the unipole and then extrapolate the types of conflict that each is likely to produce. Specifically, offensive dominance (like its defensive variant) is likely to pit the unipole against recalcitrant minor powers. Disengagement, for its part, brings with it the possibility of wars between major powers. 在此基础上，我们可以推断出单极可能采取的战略选择：进攻主导（如其防御变体）和脱离接触（如其防御变体），然后推断出每种选择可能产生的冲突类型。具体来说，进攻性主导权（如同其防御性变体）可能会使单极对抗顽抗的小国。而脱离接触则可能带来大国之间的战争。
The basic intuition behind my argument is straightforward. In bipolarity and multipolarity, alliance blocs allow disputes involving minor powers to be aggregated into broader great-power tensions. A dispute involving a great power and a lesser state tends to provoke a response by the latter’s great power sponsor, producing a confrontation between two great powers. ^(52){ }^{52} Likewise, disputes between lesser states often elicit the intervention of each side’s great power ally, again resulting in great power confrontation. These aggregation mechanisms, however, are not possible in unipolarity because there is no potential great power sponsor for a state threatened by the unipole-or by another state aligned with it. Thus, although unipolarity dampens great power competition, it produces competition between the unipole and recalcitrant minor powers and, when the unipole disengages from the world, among major and minor powers. 我的论点背后的基本直觉是直截了当的。在两极化和多极化中，联盟集团使涉及小国的争端聚集成更广泛的大国紧张局势。大国与小国之间的争端往往会引起后者的大国支持者的回应，从而导致两个大国之间的对抗。 ^(52){ }^{52} 同样，小国之间的争端往往会引起双方大国盟友的干预，从而再次导致大国对抗。然而，这些聚合机制在单极化中是不可能存在的，因为受到单极威胁的国家或与单极结盟的国家没有潜在的大国支持者。因此，尽管单极化抑制了大国竞争，但它会在单极和顽固的小国之间产生竞争，当单极脱离世界时，大国和小国之间也会产生竞争。
An emerging unipole is likely to implement a (defensive or offensive) dominance strategy, for two reasons. First is geopolitical inertia. Unipolarity is likely preceded by either bipolarity or multipolarity, both of which foster alliances with major and minor powers. ^(53){ }^{53} These alliances are likely to carry on into a unipolar world. As a result, an emerging unipole is likely to continue to engage in international affairs, at least through a strategy of defensive dominance-as reflected in the metaphors of a global policeman or night watchman often used to describe U.S. strategy throughout the 1990s. Second, a temptation to reengineer the system may lead the unipole to opt for a strategy of offensive dominance. Unipolarity minimizes structural constraints on grand strategy, and the unipole is likely to see in offensive dominance an opportunity to extract maximum benefits from its preponderance of power. ^(54){ }^{54} These two 出于两个原因，新兴单极有可能实施（防御性或进攻性）主导战略。首先是地缘政治惯性。单极化之前可能是两极化或多极化，两极化和多极化都会促进大国和小国结盟。 ^(53){ }^{53} 这些联盟可能会延续到单极世界。因此，一个新兴的单极国家很可能会继续参与国际事务，至少是通过一种防御性主导战略--这反映在整个 20 世纪 90 年代描述美国战略时经常使用的 "全球警察 "或 "守夜人 "的比喻中。其次，重塑体系的诱惑可能导致单极国家选择进攻性主导战略。单极化最大程度地减少了对大战略的结构性限制，单极国家很可能会从进攻性主导中看到从其优势力量中获取最大利益的机会。 ^(54){ }^{54} 这两个
reasons support dominance-be it defensive or offensive-as the strategy of choice for a unipole in a newly born unipolar system. ^(55){ }^{55} 在新诞生的单极体系中，单极的首选战略是主导地位--无论是防御性的还是进攻性的--。 ^(55){ }^{55}
After an initial period of dominance, however, the unipole may move toward a disengagement strategy. Two incentives may encourage such a shift. First, the wars into which either dominance strategy is likely to drag the unipole may overextend its capabilities. The unipole will increasingly see disengagement as allowing it to replenish its power. Second, the costs of such wars will rise cumulatively over time, possibly leading to the gradual emergence of domestic opposition to the unipole’s chosen strategy. My argument is not that the unipolar structure of the system predetermines such a shift, but rather that the maintenance of a dominance strategy is not predetermined by unipolarity either. 不过，经过最初的主导期后，单极可能会转向脱离战略。两种激励因素可能会鼓励这种转变。首先，无论哪种主导战略都有可能将单极拖入战争，从而过度消耗其能力。单极会越来越多地将脱离接触视为补充实力的手段。其次，随着时间的推移，这种战争的成本会逐渐上升，可能导致国内逐渐出现反对单极所选战略的声音。我的论点并不是说体系的单极结构预先决定了这种转变，而是说维持主导战略也不是由单极性预先决定的。
Furthermore, the unipole does not need to follow one of these strategies globally. It could pursue offensive dominance in one region, defensive dominance in another, and disengagement from yet another. For instance, between 1990 and 2001, the United States implemented a strategy of defensive dominance everywhere except in Africa, from which it largely disengaged after withdrawing from Somalia in 1994. Between late 2001 and 2005, when the Bush Doctrine was in full force, the United States shifted to an offensivedominance strategy in the Middle East, toppling regimes in Afghanistan and Iraq, while maintaining its defensive dominance in Europe and East Asia and remaining largely disengaged from Africa. ^(56){ }^{56} 此外，单极不需要在全球范围内遵循其中一种战略。它可以在一个地区追求进攻性主导地位，在另一个地区追求防御性主导地位，而从另一个地区脱离。例如，1990 年至 2001 年间，美国在除非洲以外的所有地区都实施了防御性主导战略，1994 年从索马里撤军后，美国基本脱离了非洲。2001年末至2005年，布什主义大行其道，美国在中东转而实施进攻主导战略，推翻了阿富汗和伊拉克政权，同时在欧洲和东亚维持防御主导地位，并在很大程度上脱离了非洲。 ^(56){ }^{56}
This diversity of strategic options available to the unipole highlights the predictive limits of structural theory. Waltz famously argued that a theory of international politics, not being a theory of foreign policy, was ill equipped to predict how particular states would act. ^(57){ }^{57} As other scholars have noted, “Polarity is at best a necessary part of an explanation rather than a sufficient explanation.” ^(58){ }^{58} A full causal account of any conflict would have to take into consideration, beyond structural incentives, the unit-level decisions that lead 单极国家战略选择的多样性凸显了结构理论在预测方面的局限性。华尔兹有一个著名的论点，他认为国际政治理论不是外交政策理论，无法预测特定国家将如何行动。 ^(57){ }^{57} 正如其他学者所指出的，"极性充其量只是解释的必要部分，而不是充分的解释"。 ^(58){ }^{58} 任何冲突的全面因果解释都必须考虑到结构性动机之外的、导致冲突的单位层面的决定。
to a breakdown in the bargaining process. Accordingly, my theory does not predict which states will become involved in conflicts in a unipolar world. Structures, however, provide incentives. In Waltz’s formulation, they "shape and shove. ^('59){ }^{\prime 59} Thus, a unipolar structure makes some states more prone to involvement in conflicts and encourages certain paths toward war. The path taken depends on the unipole’s strategy. 导致谈判破裂。因此，我的理论并不能预测在单极世界中哪些国家会卷入冲突。然而，结构提供了激励。用华尔兹的话说，它们是 "塑造和推搡"。 ^('59){ }^{\prime 59} 因此，单极结构使某些国家更容易卷入冲突，并鼓励它们走上战争的某些道路。至于走哪条路，则取决于单极的战略。
The extant view on unipolar peace presupposes that the unipole will consistently implement a strategy of defensive dominance. The next section shows how this strategy is likely to generate significant conflict. 关于单极和平的现有观点预先假定，单极将始终实施防御性主导战略。下一节将说明这一战略如何可能引发重大冲突。
Defensive Dominance 防守优势
A unipole carrying out a defensive-dominance strategy will seek to preserve all three aspects of the status quo: maintaining the territorial boundaries and international political alignments of all other states, as well as freezing the global distribution of power. ^(60){ }^{60} This strategy can lead to conflict in two ways, both of which stem from uncertainty about the unipole’s intentions. First, not knowing the extent of the unipole’s determination to pursue a strategy of defensive dominance may spur some minor powers to develop their capabilities. Second, uncertainty about the degree to which the unipole will oppose small changes to the status quo may lead some minor powers to attempt them. In both cases, the opposition of the unipole to these actions is likely to lead to war. In this section, I lay out these two pathways to conflict and then illustrate them with historical examples. 实施防御主导战略的单极国将寻求维持现状的所有三个方面：维持所有其他国家的领土疆界和国际政治结盟，以及冻结全球权力分配。 ^(60){ }^{60} 这种战略会通过两种方式导致冲突，而这两种方式都源于对单极意图的不确定性。首先，不知道单极在多大程度上决心奉行防御性主导战略，可能会刺激一些小国发展自己的能力。其次，不确定单极在多大程度上会反对对现状的微小改变，可能会导致一些小国试图改变现状。在这两种情况下，单极对这些行动的反对都有可能导致战争。在本节中，我将阐述这两种冲突途径，然后用历史实例加以说明。
To be sure, states can never be certain of other states’ intentions. ^(61){ }^{61} There are a couple of reasons, however, why this uncertainty increases in unipolarity, even when the unipole appears to be determined to maintain the status quo. First, other states cannot be certain that the unipole will always pursue nonrevisionist goals. This is particularly problematic because unipolarity minimizes the structural constraints on the unipole’s grand strategy. As Waltz writes, "Even if a dominant power behaves with moderation, restraint, and forbearance, weaker states will worry about its future behavior. . . . The absence of se- 可以肯定的是，国家永远无法确定其他国家的意图。 ^(61){ }^{61} 然而，有几个原因可以解释为什么这种不确定性在单极状态下会增加，即使单极似乎决心维持现状。首先，其他国家无法确定单极会始终追求非前瞻性目标。这一点尤其成问题，因为单极化将对单极国家大战略的结构性限制降至最低。正如华尔兹所写："即使一个主导大国表现得温和、克制和忍让，弱小国家也会担心它未来的行为......"。. . ......."。
rious threats to American security gives the United States wide latitude in making foreign policy choices." ^(162){ }^{162} Second, unipolarity takes away the principal tool through which minor powers in bipolar and multipolar systems deal with uncertainty about great power intentions-alliances with other great powers. Whereas in these other systems minor powers can, in principle, attenuate the effects of uncertainty about great power intentions through external balancing, in a unipolar world no great power sponsor is present by definition. In effect, the systemic imbalance of power magnifies uncertainty about the unipole’s intentions. ^(63){ }^{63} 美国安全面临的巨大威胁使美国在外交政策选择上有了很大的自由度。 ^(162){ }^{162} 其次，单极化使两极和多极体系中的小国失去了应对大国意图不确定性的主要工具--与其他大国结盟。在其他体系中，小国原则上可以通过外部平衡来削弱大国意图不确定性的影响，而在单极世界中，根据定义，不存在大国赞助者。实际上，系统性的力量失衡放大了单极意图的不确定性。 ^(63){ }^{63}
Faced with this uncertainty, other states have two options. First, they can accommodate the unipole and minimize the chances of conflict but at the price of their external autonomy. ^(64){ }^{64} Accommodation is less risky for major powers because they can guarantee their own survival, and they stand to benefit greatly from being part of the unipolar system. ^(65){ }^{65} Major powers are therefore unlikely to attempt to revise the status quo. Minor powers are also likely to accommodate the unipole, in an attempt to avoid entering a confrontation with a preponderant power. Thus, most states will accommodate the unipole because, as Wohlforth points out, the power differential rests in its favor. ^(66){ }^{66} 面对这种不确定性，其他国家有两种选择。首先，它们可以迁就单极国家，将冲突的可能性降到最低，但代价是丧失对外自主权。 ^(64){ }^{64} 对于大国来说，迁就的风险较小，因为它们可以保证自己的生存，而且作为单极体系的一部分，它们可以从中获益良多。 ^(65){ }^{65} 因此，大国不太可能试图改变现状。小国也可能会迁就单极，以避免与强国发生对抗。因此，大多数国家都会迁就单极，因为正如沃尔福思（Wohlforth）所指出的，实力差距对单极有利。 ^(66){ }^{66}
Accommodation, however, entails greater risks for minor powers because their survival is not assured if the unipole should turn against them. Thus some of them are likely to implement a second strategic option-resisting the unipole. 然而，对小国来说，通融会带来更大的风险，因为如果单极反过来对付它们，它们的生存就没有保障。因此，一些小国可能会采取第二种战略选择--抵抗单极。
The structure of the international system does not entirely determine whether or not a minor power accommodates the unipole. Still, structure conditions the likelihood of accommodation in two ways. To begin, a necessary part of a strategy of dominance is the creation of alliances or informal security commitments with regional powers. Such regional powers, however, are likely to have experienced conflict with, or a grievance toward, at least some of its neighboring minor powers. The latter are more likely to adopt a recalcitrant posture. Additionally, by narrowing their opportunities for regional integration and security maximization, the unipole’s interference with the regional balance of power is likely to lower the value of the status quo for these minor powers. ^(67){ }^{67} As the literature on the “value of peace” shows, countries that attribute a low value to the status quo are more risk acceptant. This argument helps explain, for example, Japan’s decision to attack the United States in 1941 and Syria’s and Egypt’s decision to attack Israel in 1973. ^(68){ }^{68} In both cases, aggressor states knew that their capabilities were significantly weaker than those of their targets. They were nonetheless willing to run the risk of launching attacks because they found the prewar status quo unacceptable. ^(69){ }^{69} Thus, for these states, the costs of balancing were lower relative to those of bandwagoning. 国际体系的结构并不完全决定小国是否迁就单极。不过，结构在两个方面决定了妥协的可能性。首先，称霸战略的一个必要组成部分是与地区大国建立联盟或做出非正式的安全承诺。然而，这些地区大国很可能至少与周边一些小国发生过冲突，或对这些小国心怀不满。后者更有可能采取顽抗的姿态。此外，单极国家对地区力量平衡的干预缩小了这些国家实现地区一体化和安全最大化的机会，很可能会降低这些小国维持现状的价值。 ^(67){ }^{67} 正如有关 "和平价值 "的文献所显示的那样，对现状评价较低的国家更容易接受风险。例如，这一论点有助于解释日本在 1941 年攻击美国的决定，以及叙利亚和埃及在 1973 年攻击以色列的决定。 ^(68){ }^{68} 在这两个案例中，侵略国都知道自己的能力远远弱于目标。尽管如此，它们仍愿意冒险发动攻击，因为它们认为战前现状是不可接受的。 ^(69){ }^{69} 因此，对这些国家来说，平衡的代价要低于拉帮结派的代价。
In an international system with more than one great power, recalcitrant minor powers would, in principle, be able to balance externally by finding a great power sponsor. ^(70){ }^{70} In unipolarity, however, no such sponsors exist. ^(71){ }^{71} Only major powers are available, but because their survival is already guaranteed, they are likely to accommodate the unipole. And even if some do not, they are unlikely to meet a recalcitrant minor power’s security needs given that they possess 在一个拥有不止一个大国的国际体系中，顽固的小国原则上可以通过找到一个大国赞助者来实现外部平衡。 ^(70){ }^{70} 然而，在单极化中，不存在这样的赞助者。 ^(71){ }^{71} 只有大国可以提供赞助，但由于它们的生存已经有了保障，它们很可能会迁就单极。即使有些大国不这样做，它们也不太可能满足顽固的小国的安全需求，因为它们拥有
only limited power-projection capabilities. ^(72){ }^{72} As such, recalcitrant minor powers must defend themselves, which puts them in a position of extreme selfhelp. 只有有限的力量投射能力。 ^(72){ }^{72} 因此，顽抗的小国必须自卫，这使它们处于极端自救的境地。
There are four characteristics common to states in this position: (1) anarchy, (2) uncertainty about other states’ intentions, (3) insufficient capabilities to deter a great power, and (4) no potential great power sponsor with whom to form a balancing coalition. The first two characteristics are common to all states in all types of polarity. The third is part of the rough-and-tumble of minor powers in any system. The fourth, however, is unique to recalcitrant minor powers in unipolarity. This dire situation places recalcitrant minor powers at risk for as long as they lack the capability to defend themselves. They depend on the goodwill of the unipole and must worry that the unipole will shift to a strategy of offensive dominance or disengagement. Recalcitrant minor powers will therefore attempt to bolster their capabilities through internal balancing. 处于这种地位的国家有四个共同特征：(1) 无政府状态，(2) 对其他国家意图的不确定性，(3) 没有足够能力威慑大国，(4) 没有潜在的大国赞助者与之结成平衡联盟。前两个特征是所有极化类型国家的共同特征。第三个特点则是任何体系中小国的坎坷经历。然而，第四个特点是单极化中顽固的小国所独有的。只要顽固的小国缺乏自卫能力，这种严峻形势就会使它们处于危险之中。它们依赖于单极的善意，必须担心单极会转向进攻性主导战略或脱离接触。因此，倔强的小国将试图通过内部平衡来增强自身能力。
To deter an eventual attack by the unipole and bolster their chances of survival in the event deterrence fails, recalcitrant minor powers will attempt to reinforce their conventional defenses, develop the most effective asymmetric strategies possible, and, most likely in the nuclear age, try to acquire the ultimate deterrent-survivable nuclear weapons. ^(73){ }^{73} In so doing, they seek to become major powers. 为了阻止单极的最终攻击，并在威慑失败时增加自己的生存机会，顽固的小国会试图加强常规防御，发展最有效的非对称战略，而在核时代，最有可能的是试图获得终极威慑力量--可生存的核武器。 ^(73){ }^{73} 在这样做的过程中，它们试图成为大国。
Defensive dominance, however, also gives the unipole reason to oppose any such revisions to the status quo. First, such revisions decrease the benefits of systemic leadership and limit the unipole’s ability to convert its relative power advantage into favorable outcomes. In the case of nuclear weapons, this limitation is all but irreversible, virtually guaranteeing the recalcitrant regime immunity against any attempt to coerce or overthrow it. Second, proliferation has the potential to produce regional instability, raising the risk of arms races. These would force the unipole to increase defense spending or accept a narrower overall relative power advantage. Third, proliferation would lead to the 然而，防御性主导地位也使单极有理由反对对现状的任何修改。首先，这种修改会减少系统性领导的好处，限制单极将其相对实力优势转化为有利结果的能力。就核武器而言，这种限制几乎是不可逆转的，几乎保证了顽固政权免受任何胁迫或推翻的企图。其次，核扩散有可能造成地区不稳定，增加军备竞赛的风险。这将迫使单极国家增加国防开支，或接受更小的总体相对实力优势。第三，扩散会导致
emergence of a recalcitrant major power that could become the harbinger of an unwanted large-scale balancing attempt. 出现一个顽固的大国，这可能会成为不受欢迎的大规模平衡企图的先兆。
The unipole is therefore likely to demand that recalcitrant minor powers not revise the status quo. The latter, however, will want to resist such demands because of the threat they pose to those states’ security. ^(74){ }^{74} Whereas fighting over such demands would probably lead to defeat, conceding to them peacefully would bring the undesired outcome with certainty. A preventive war is therefore likely to ensue. 因此，单极国家可能会要求顽固不化的小国不要改变现状。然而，后者会抵制这种要求，因为它们会对这些国家的安全构成威胁。 ^(74){ }^{74} 为这些要求而战很可能会导致失败，而和平让步则肯定会带来意想不到的结果。因此，一场预防性战争很可能会接踵而至。
In the second causal path to war, recalcitrant minor powers test the limits of the status quo by making small revisions-be they territorial conquests, altered international alignments, or an increase in relative power-evocative of Thomas Schelling’s famous "salami tactics."75 The unipole may not, however, accept these revisions, and instead demand their reversal. For a variety of reasons, including incomplete information, commitment problems, and the need for the minor power to establish a reputation for toughness, such demands may not be heeded. As a result, war between the unipole and recalcitrant minor powers emerges as a distinct possibility. ^(76){ }^{76} 在通往战争的第二条因果路径中，顽固的小国通过小幅调整来试探现状的极限--无论是领土征服、国际结盟的改变，还是相对实力的增强--这与托马斯-谢林（Thomas Schelling）著名的 "萨拉米战术"（salami tactics）不谋而合。由于种种原因，包括信息不完整、承诺问题以及小国需要建立强硬声誉，这些要求可能不会被理睬。因此，单极大国与顽固不化的小国之间的战争很有可能发生。 ^(76){ }^{76}
Regardless of the causal path, a war between the unipole and a recalcitrant minor power creates a precedent for other recalcitrant minor powers to boost their own capabilities. Depending on the unipole’s overall capabilities-that is, whether it can launch a second simultaneous conflict-it may also induce other recalcitrant minor powers to accelerate their balancing process. Thus, a war against a recalcitrant minor power presents other such states with greater incentives for, and (under certain conditions) higher prospects of, assuring their survival by acquiring the necessary capabilities, including nuclear weapons. 无论因果关系如何，单极与倔强的小国之间的战争都为其他倔强的小国提升自身能力开创了先例。根据单极国家的整体能力，即它是否能同时发动第二次冲突，它也可能促使其他倔强的小国加快平衡进程。因此，对倔强的小国发动战争会给其他此类国家带来更大的动力，（在某些条件下）也会给它们带来更高的前景，即通过获取必要的能力（包括核武器）来确保自己的生存。
At the same time, and depending on the magnitude of the unipole’s power preponderance, a war against a recalcitrant minor power creates an opportunity for wars among major and minor powers-including major power wars. To the extent that the unipole’s power preponderance is limited by its engagement in the first war, its ability to manage confrontations between other states elsewhere is curtailed, increasing the chances that these will erupt into mili- 与此同时，根据单极力量优势的大小，对顽抗的小国发动战争会为大国和小国之间的战争--包括大国战争--创造机会。如果单极国家的力量优势因参与第一场战争而受到限制，那么它在其他地方管理其他国家之间对抗的能力就会受到削弱，从而增加这些对抗爆发为军事冲突的可能性。
tary conflicts. Therefore, even when the unipole is engaged, war remains a possibility. 战争冲突。因此，即使在单极参与的情况下，战争仍有可能发生。
Between the end of the Cold War and the terrorist attacks of September 11, 2001, the United States generally implemented a strategy of defensive dominance. During this period, the dynamics described in this section can be seen at work in the cases of the 1991 Persian Gulf War and the 1999 Kosovo War, as well as in the Kargil War between India and Pakistan, and in North Korea’s and Iran’s nuclear programs. 从冷战结束到 2001 年 9 月 11 日的恐怖袭击，美国总体上实施了防御性主导战略。在此期间，1991 年的波斯湾战争、1999 年的科索沃战争、印度和巴基斯坦之间的卡吉尔战争以及朝鲜和伊朗的核计划都体现了本节所描述的动态。
On August 2, 1990, Saddam Hussein ordered his forces to invade Kuwait, convinced the United States would not oppose this revision of the status quo. During the months that followed, the United States assembled an international coalition determined to restore Kuwaiti independence, and it obtained UN authorization to use force if Iraq did not withdraw its occupation forces by January 15,1991 . Two days after this deadline, the U.S.-led coalition began military action against Iraqi forces, expelling them from Kuwait in six weeks. ^(77){ }^{77} 1990 年 8 月 2 日，萨达姆-侯赛因下令入侵科威特，他相信美国不会反对这一改变现状的行动。在随后的几个月里，美国组建了一个决心恢复科威特独立的国际联盟，并获得了联合国的授权，如果伊拉克不在 1991 年 1 月 15 日之前撤出其占领军，就可以使用武力。在这一最后期限两天后，以美国为首的联盟开始对伊拉克军队采取军事行动，并在六周内将其驱逐出科威特。 ^(77){ }^{77}
Two points deserve mention. First, the Gulf War was triggered by Iraq’s miscalculation regarding whether the United States would accept Iraqi annexation of Kuwait. At the outset of the unipolar era, great uncertainty surrounded the limits of what actions U.S. decisionmakers would find permissible. ^(78){ }^{78} Iraq miscalculated the degree of U.S. flexibility, and war ensued. Second, the war was made possible by unipolarity, which placed Iraq in a situation of extreme selfhelp. Indeed, lack of a great power sponsor-at the time, the Soviet Union was in strategic retrenchment-was duly noted in Baghdad. Immediately after the war, Saddam’s foreign minister, Tariq Aziz, lamented, "We don’t have a patron anymore. . . . If we still had the Soviets as our patron, none of this would have happened."79 有两点值得一提。首先，海湾战争是由伊拉克对美国是否会接受伊拉克吞并科威特的错误判断引发的。在单极时代开始之初，美国决策者认为哪些行动是可以允许的存在很大的不确定性。 ^(78){ }^{78} 伊拉克错误地估计了美国的灵活程度，战争随之爆发。其次，单极化使战争成为可能，这使伊拉克处于极端自救的境地。事实上，缺乏大国支持--当时苏联正在进行战略收缩--在巴格达得到了应有的重视。战后不久，萨达姆的外交部长塔里克-阿齐兹就哀叹道："我们再也没有靠山了。. . .如果我们还有苏联作为靠山，这一切都不会发生 "79。
Similarly, in 1999, Serbian leaders miscalculated U.S. tolerance to ethnic violence in Kosovo, a secessionist province of the Federal Republic of Yugoslavia. 同样，1999 年，塞尔维亚领导人错误估计了美国对南斯拉夫联盟共和国分离主义省份科索沃境内种族暴力的容忍度。
In March 1999, reacting to increasing brutality in the province, the international community convened a conference, which produced the Rambouillet accords. This agreement called for the restoration of Kosovo’s autonomy and the deployment of NATO peacekeeping forces, both unacceptable to Serbian authorities, who refused to submit to it. ^(80){ }^{80} In response, NATO launched a bombing campaign in Yugoslavia. In early June, after nine weeks of bombing, NATO offered the Serbian leadership a compromise, which it accepted, ending the war. ^(81){ }^{81} 1999 年 3 月，针对该省日益严重的暴行，国际社会召开了一次会议，达成了《朗布依埃协定》。该协议要求恢复科索沃自治，并部署北约维和部队，这两点都是塞尔维亚当局所不能接受的，他们拒绝服从该协议。 ^(80){ }^{80} 作为回应，北约在南斯拉夫发动了轰炸行动。6月初，经过9周的轰炸，北约向塞尔维亚领导人提出了妥协方案，塞尔维亚领导人接受了这一方案，战争就此结束。 ^(81){ }^{81}
Once the war had started and it became clear that Serbia had overreached, Belgrade relied on the support of its ancestral major power ally, Russia. Serbian strategy during the war thus aimed in part at buying time for Russia to increase pressure on NATO to cease hostilities. Contrary to Belgrade’s expectations, however, Russian support for Serbian aims eroded as the war continued. On May 6, Russia agreed with the Group of Seven nations on a plan that included the deployment of UN peacekeepers and a guarantee of Yugoslavia’s territorial integrity. By mid-May, faced with Serbia’s obduracy, Moscow began to press its ally to accept the offer. Thus, not only did Russian support fail to prevent a U.S.-led intervention, but it was instrumental in convincing Serbia to accede to NATO’s demands. ^(82){ }^{82} 一旦战争打响，塞尔维亚显然走得太远，贝尔格莱德就会依靠其祖先的大国盟友俄罗斯的支持。因此，塞尔维亚在战争期间的战略部分旨在为俄罗斯争取时间，以加大对北约的压力，迫使其停止敌对行动。然而，与贝尔格莱德的期望相反，随着战争的持续，俄罗斯对塞尔维亚目标的支持逐渐减弱。5月6日，俄罗斯与七国集团就一项计划达成一致，其中包括部署联合国维和人员和保证南斯拉夫的领土完整。到 5 月中旬，面对塞尔维亚的顽固不化，莫斯科开始迫使其盟友接受这一提议。因此，俄罗斯的支持不仅未能阻止美国领导的干预，反而在说服塞尔维亚接受北约要求方面发挥了重要作用。 ^(82){ }^{82}
The only war between major powers to have occurred thus far in a unipolar world-the Kargil War between India and Pakistan-started, as my theory would have predicted, while the United States was involved in Kosovo. ^(83){ }^{83} In May 1999, India detected Pakistani forces intruding into the Kargil sector in Indian-controlled Kashmir. This action triggered the first Indo-Pakistani war of the nuclear age, which ended on July 4-after the cessation of military operations in Kosovo-when President Bill Clinton demanded Pakistan’s withdrawal, which occurred on July 26. ^(84){ }^{84} 正如我的理论所预测的那样，迄今为止在单极世界中发生的唯一一场大国之间的战争--印度和巴基斯坦之间的卡吉尔战争--是在美国卷入科索沃问题时爆发的。 ^(83){ }^{83} 1999年5月，印度发现巴基斯坦军队侵入印控克什米尔的卡吉尔地区。这一行动引发了核时代的第一次印巴战争，战争于7月4日--科索沃军事行动停止后--结束，当时比尔-克林顿总统要求巴基斯坦撤军，巴基斯坦于7月26日撤军。 ^(84){ }^{84}
In the absence of a great power sponsor and uncertain of U.S. intentions, 在没有大国支持和不确定美国意图的情况下、
Iran and North Korea-both recalcitrant minor powers-have made considerable efforts to bolster their relative power by developing a nuclear capability. Unsurprisingly, the United States has consistently opposed their efforts, but has so far been unable to persuade either to desist. 伊朗和朝鲜这两个顽固的小国都做出了巨大努力，通过发展核能力来增强自己的相对实力。不出所料，美国一直反对它们的努力，但迄今为止仍无法说服其中任何一方放弃。
The North Korean nuclear program dates to the 1960s, but most of the nuclear development was conducted in a world with a status quo unipole. ^(85){ }^{85} Throughout the 1990s and into the early 2000s, North Korea sought to elude U.S. opposition without ever crossing the nuclear threshold. The North Korean regime seemed to have understood that the United States would view an explicit move toward a nuclear breakout as an extreme provocation and raise the possibility of a preventive war. When the United States shifted to a strategy of offensive dominance in late 2001, however, Pyongyang wasted little time in acquiring its nuclear deterrent. 朝鲜的核计划可以追溯到 20 世纪 60 年代，但大部分核开发都是在单极现状下进行的。 ^(85){ }^{85} 在整个 20 世纪 90 年代到 21 世纪初，朝鲜一直试图在不跨越核门槛的情况下躲避美国的反对。朝鲜政权似乎已经明白，美国会将明确的核突破行动视为极端挑衅，并引发预防性战争的可能性。然而，当美国在 2001 年末转向进攻性主导战略时，平壤几乎没有浪费时间就获得了核威慑力量。
Iran, too, pursued a nuclear program throughout the 1990s. ^(86){ }^{86} The Iranian nuclear program, started in the 1950s, gained new impetus with the end of the Cold War as the result of a confluence of factors: the 1989 replacement of an antinuclear supreme leader, Ayatollah Ruhollah Khomeini, with a pronuclear Ayatollah Ali Khamenei; the discovery of Iraq’s covert nuclear program during the 1991 Gulf War; and, above all, an increased U.S. presence in the region following that war. ^(87){ }^{87} A decade later, the expansion of Iran’s nuclear program prompted the State Department to proclaim, “We believe Iran’s true intent is to develop the capability to produce fissile material for nuclear weapons.” ^(18){ }^{18} Iran’s nuclear program continued throughout the period in which the United States shifted toward a strategy of offensive dominance, to which I turn next. 伊朗也在整个 20 世纪 90 年代推行核计划。 ^(86){ }^{86} 伊朗的核计划始于 20 世纪 50 年代，随着冷战的结束，伊朗的核计划获得了新的动力，这是多种因素共同作用的结果：1989 年，反核的最高领袖阿亚图拉-鲁霍拉-霍梅尼被代核的阿亚图拉-阿里-哈梅内伊取代；1991 年海湾战争期间，伊拉克的秘密核计划被发现；最重要的是，战争结束后，美国在该地区的存在有所增加。 ^(87){ }^{87} 十年后，伊朗核计划的扩张促使美国国务院宣称："我们相信伊朗的真正意图是发展生产核武器用裂变材料的能力。 ^(18){ }^{18} 在美国转向进攻性主导战略的整个时期，伊朗的核计划仍在继续。
Offensive Dominance 进攻优势
A unipole carrying out an offensive-dominance strategy wants to revise the status quo in its favor by acquiring more territory, by favorably changing the alignment of other states, or by altering the distribution of power in its own benefit-or some combination of these. 实施进攻主导战略的单极国家希望通过获取更多领土、有利地改变其他国家的结盟或改变权力分配来改变现状，使之对自己有利，或者是通过这些方式的组合来改变现状。
Territorial conquest, which is the most ambitious goal of an offensivedominance strategy, is a daunting task in an age of nationalism and is thus 征服领土是进攻主导战略最雄心勃勃的目标，在民族主义盛行的时代，这是一项艰巨的任务，因此
likely to be rare. ^(89){ }^{89} Efforts to alter the international alignments of other states or the balance of power can be pursued through soft power and persuasion, but this is unlikely to prove sufficient, and the unipole may decide to use force. ^(90){ }^{90} 可能很少见。 ^(89){ }^{89} 可以通过软实力和劝说来改变其他国家的国际联盟或力量平衡，但这不太可能被证明是足够的，单极可能会决定使用武力。 ^(90){ }^{90}
By putting recalcitrant minor powers in a position of extreme-self help, an offensive-dominance strategy triggers two pathways to conflict. In both cases, a deterrence breakdown leads to a preventive war. 进攻主导战略将顽固不化的小国置于极端自助的境地，从而引发两种冲突途径。在这两种情况下，威慑崩溃都会导致预防性战争。
Following the first pathway: the unipole makes revisionist demands that recalcitrant minor powers are unlikely to accept peacefully, because these pose a threat to their survival. Given its preponderance of power, the unipole may decide to go to war. 按照第一种途径：单极提出修正主义要求，而顽固的小国不太可能和平接受，因为这些要求对其生存构成威胁。鉴于其力量的优势，单极可能会决定开战。
The second causal pathway follows a slightly more complex logic. Like its defensive version, a strategy of offensive dominance provides strong incentives for recalcitrant minor powers to balance internally. These attempts to bolster their relative power, however, are likely to lead to war with the unipole before the recalcitrant power is able to acquire additional capabilities. The reason for this outcome is that the unipole will oppose any attempt by minor powers to revise the status quo in a way that is detrimental to its interests. 第二种因果途径的逻辑稍显复杂。与防御性战略一样，进攻性主导战略也为顽抗的小国提供了内部平衡的强大动力。然而，这些增强相对实力的尝试很可能会在倔强大国获得更多能力之前导致与单极国家的战争。造成这种结果的原因是，单极国将反对小国以损害其利益的方式改变现状的任何企图。
In addition, wars pitting a recalcitrant minor power against a unipole implementing a strategy of offensive dominance have two effects common to defensive dominance. First, they encourage other recalcitrant minor powers to redouble their balancing efforts. Second, they may make room for wars among major and minor powers. 此外，一个顽固的小国与一个实施进攻性主导战略的单极国家之间的战争有两种与防御性主导战略相同的效果。首先，它们鼓励其他顽固的小国加倍努力保持平衡。其次，它们可能为大国和小国之间的战争创造空间。
Reacting to the September 11 terrorist attacks, the United States adopted a strategy of offensive dominance in the Middle East. Although this short period has produced only a slim empirical record that can be harnessed to support my theory, the mechanisms I posit can best be seen at work in the 2003 U.S.-led invasion of Iraq. The United States’ goal was to revise Iraq’s international alignment and decrease its relative power by installing an accommodating regime in Baghdad and ending Saddam’s putative weapons of mass destruction (WMD) program. ^(91){ }^{91} 针对 9-11 恐怖袭击事件，美国在中东采取了进攻性主导战略。虽然这一时期很短，只有少量的经验记录可以用来支持我的理论，但我所假设的机制在 2003 年美国领导的入侵伊拉克行动中得到了最好的体现。美国的目标是在巴格达建立一个包容的政权，结束萨达姆的大规模杀伤性武器计划，从而改变伊拉克的国际格局，削弱其相对实力。 ^(91){ }^{91}
In the end, no WMD were found after the invasion. ^(92){ }^{92} Still, Saddam had pos- 最终，入侵后没有发现大规模杀伤性武器。 ^(92){ }^{92} 尽管如此，萨达姆仍有可能--...
sessed a nuclear program, which he stopped only grudgingly when UNimposed sanctions in the aftermath of the 1991 Gulf War made it impossible to acquire the materials and technology needed for a nuclear deterrent. ^(93){ }^{93} Indeed, the possibility of Iraq acquiring nuclear weapons, which Washington was convinced would soon become a reality, featured prominently in the George W. Bush administration’s argument for going to war. ^(94){ }^{94} 1991年海湾战争后，联合国对伊拉克实施制裁，使其无法获得核威慑所需的材料和技术，伊拉克才勉强停止了核计划。 ^(93){ }^{93} 事实上，伊拉克获得核武器的可能性在小布什政府发动战争的论据中占据了突出位置，而华盛顿方面确信这种可能性很快就会成为现实。 ^(94){ }^{94}
Although confronted with an imminent invasion, Saddam refused to back down. His rationale seems to have been based on his estimate that, first, France or Russia would intercede on Iraq’s behalf, preventing war and, second, if that failed, Iraqi forces would be capable of increasing the military costs for the United States to the point at which American public opinion would force Washington to back down. ^(95){ }^{95} None of this happened. China, France, and Russia-all major powers-did oppose UN authorization to use force against Iraq, but when the United States displayed an unequivocal determination to invade anyway, no major power did much to stop it. ^(96){ }^{96} Ultimately, U.S.-led coalition troops toppled Saddam’s regime in three weeks, and major military operations ended within a month of the invasion date. 尽管面对迫在眉睫的入侵，萨达姆拒绝退让。他的理由似乎是基于这样的估计：首先，法国或俄罗斯会代表伊拉克出面调停，阻止战争；其次，如果调停失败，伊拉克军队将有能力增加美国的军事成本，以至于美国舆论迫使华盛顿让步。 ^(95){ }^{95} 这些都没有发生。中国、法国和俄罗斯--这些大国都反对联合国授权对伊拉克动武，但当美国明确表示无论如何都要入侵伊拉克时，没有一个大国采取任何行动加以阻止。 ^(96){ }^{96} 最终，以美国为首的联军在三周内推翻了萨达姆政权，主要军事行动也在入侵日期后一个月内结束。
The Iraq War also led other recalcitrant minor powers to accelerate their proliferation attempts. Having been identified by President Bush, alongside Iraq, as members of the “axis of evil,” Iran and North Korea were particularly quick to respond. ^(97){ }^{97} A mere two weeks after the fall of Baghdad, Pyongyang officials informed their American counterparts that North Korea possessed nuclear weapons, making the country immune to any U.S. attempts to depose its regime. ^(98){ }^{98} Iran, too, has ramped up its nuclear program since 2002 and is likely to continue pursuing a nuclear capability while trying to avoid preventive action 伊拉克战争还导致其他顽固不化的小国加快了扩散企图。伊朗和朝鲜被布什总统认定为 "邪恶轴心"，与伊拉克同属 "邪恶轴心"，它们的反应尤其迅速。 ^(97){ }^{97} 巴格达沦陷仅两周后，平壤官员就告知美国同行，朝鲜拥有核武器，因此美国试图推翻朝鲜政权的任何行动都将使朝鲜免受影响。 ^(98){ }^{98} 伊朗自 2002 年以来也加大了核计划的力度，并很可能在试图避免预防性行动的同时继续追求核能力。
by the United States. ^(99){ }^{99} Unfortunately for the prospects of peace, it is also likely the United States will oppose this development and, if necessary, resort to the use of force. ^(100){ }^{100} 美国。 ^(99){ }^{99} 不幸的是，对和平前景而言，美国也很可能会反对这一事态发展，并在必要时诉诸武力。 ^(100){ }^{100}
Disengagement 脱离接触
Disengagement requires the unipole to avoid interfering with the balance of power in regions other than its own. (The unipole cannot disengage from its own region.) Such a strategy decreases tensions between the unipole and other states, making wars involving the unipole less likely, but it also makes room for conflicts among competing major and minor powers. 脱离接触要求单极国家避免干预其所在区域以外的力量平衡（单极国家不能脱离其所在区域）。(这种战略会降低单极与其他国家之间的紧张关系，从而减少涉及单极的战争的可能性，但同时也为相互竞争的大国和小国之间的冲突留出了空间。
Given the great-power vacuum created by a disengaged unipole, each region beyond the unipole’s can be treated as a small-scale quasi system unto itself. The regions from which the unipole disengages are, in effect, insulated from the global mechanisms of conflict created directly by a unipolar structure. These regions can be unipolar, bipolar, or multipolar. Interaction between major powers in each of them will be governed by the dynamics that regulate great power interaction in unipolar, bipolar, or multipolar systems. 由于单极脱钩造成了大国真空，单极以外的每个地区都可以被视为一个小规模的准体系。单极脱离的地区实际上与单极结构直接造成的全球冲突机制绝缘。这些地区可以是单极、两极或多极。每一个地区大国之间的互动都将受制于单极、两极或多极体系中大国互动的动力。
Unipolar regions beyond the unipole’s own should be rare. Even a disengaged unipole is likely to feel threatened by the emergence of a regional hegemon in another major region of the globe. (In fact, such a regional hegemon rising in an important region would qualify as a peer competitor, reestablishing the systemic balance of power and putting an end to unipolarity.) It is possible, however, that in peripheral areas of the globe regional unipolarity would emerge without upsetting a disengaged unipole. I call this situation "nested unipolarity."101 单极以外的单极地区应该很少见。即使是脱离单极的国家，也可能会因为全球另一个主要地区出现地区霸主而感到威胁。(事实上，在一个重要地区崛起的地区霸主将成为同级竞争者，重建系统性力量平衡，结束单极状态）。然而，也有可能在全球的边缘地区出现地区单极，而不会破坏脱离的单极。我称这种情况为 "嵌套单极化 "101。
In a nested unipolar region from which the global unipole nonetheless remains disengaged, conflict-producing dynamics will emerge, along the lines of those described above in the sections about strategies of offensive and defensive dominance. Given uncertainty about its intentions, a strategy of defensive dominance on the part of a regional hegemon will also trigger pathways to 在一个嵌套的单极地区，如果全球单极仍然脱离该地区，就会出现与上文关于进攻性和防御性主导战略的章节中所描述的类似的引发冲突的动态。鉴于其意图的不确定性，地区霸主的防御性主导战略也会引发以下途径
conflict in the region. ^(102){ }^{102} Similarly, a regional unipolar power that pursues a strategy of offensive dominance should generate regionally the same conflictproducing mechanisms that were described above at the global level. 地区冲突。 ^(102){ }^{102} 同样，一个奉行进攻性主导战略的地区单极强国也会在地区范围内产生与上述全球层面相同的冲突制造机制。
The remaining regions will be either bipolar or multipolar. No consensus exists on their comparative peacefulness. ^(103){ }^{103} In fact, there are plausible causal mechanisms accounting for conflict in both types of system. One can therefore expect that both bipolar and multipolar regions will feature significant levels of conflict-involving minor and major powers-when left on their own. 其余地区要么是两极，要么是多极。关于它们的相对和平程度，目前尚无共识。 ^(103){ }^{103}