霸权的逻辑：美国亚太安全战略的多边转向

二战后，美国在亚太地区构筑起双边联盟体系，但近年来对于加强多边安全合作更为积极。美国近几届政府在亚太安全战略方面作出了重大调整，从奥巴马政府到拜登政府都在推动双边合作转向多边合作，而为何发生这一转变值得探讨。美国在权力优势明显时，倾向于采取双边合作；当美国权力优势缩小时，更加重视多边合作，其安全合作形式是接近于联盟还是相对松散的安全合作，则取决于外部威胁性质和内部分歧大小。美国亚太安全合作形式的调整取决于中美实力差距、外部威胁变化和成员国分歧，多边形式可以更大范围地进行国际动员，最大程度地维护自身的霸权地位。美国在亚太地区的多边安全合作拥有稳固的合作基础、灵活的多边形式和共同的身份认同，有助于美国调动战略资源和联合应对共同关注的威胁。亚太多边安全合作增强了美国的安全动员能力，冲击了亚太地区秩序，给中国带来较大的安全压力。但不同合作机制也面临合作程度不一、成员战略分歧和合作议题分散的影响，合作进程存在着不确定性。

Logic of Hegemony: The Multilateral Transformation of the US Asia-Pacific Security Strategy

After the end of World War II, the US successfully built a network of bilateral alliances in the Asia-Pacific region. In recent years, it has become more active in strengthening multilateral security cooperation. From the Obama administration to the Biden administration, the US government has made significant adjustments in its Asia-Pacific security strategy, pushing for a shift from bilateralism to multilateralism. It is worth exploring the reason why the shift has occurred. The US tends to promote bilateral cooperation when it has a huge power advantage. When its power advantage shrinks, it places greater emphasis on multilateral cooperation. Whether its security cooperation is prone to forge alliances or adopt a relatively loose form of security cooperation depends on the nature of external threats and the degree of internal disagreements. The adjustment of forms of US security cooperation in the Asia-Pacific region results from the narrowing power gap between China and the US, changes in external threats and disagreements among its allies. The multilateral form of security cooperation offers the US a greater capacity to mobilize its allies and maintain its hegemonic position. The US-Japan-ROK trilateral cooperation, the AUKUS trilateral security partnership, the Five Eyes and the Quad are all typical examples of the US efforts to shift from bilateralism to multilateralism. The US multilateral security cooperation in the Asia-Pacific region boasts a solid foundation, a common identity and a variety of flexible cooperative forms that help the United States mobilize strategic resources and unite other countries to address threats of common concern. In a word, the multilateral security cooperation has greatly enhanced the US security mobilization capabilities, which exerts huge impact on the order of the Asia-Pacific region and puts greater security pressure on China. However, different cooperation mechanisms also witness different depths of cooperation and suffer from divergences among their members as well as fragmented cooperation-related issues.