第二次世界大戰結束以後，以美國為首的西方國家為了嚇阻蘇聯的入侵，遂成立了北大西洋公約組織。這也標誌著冷戰時期美蘇兩強對峙的局面。冷戰結束以後，許多學者因而預言北約即將瓦解。但多年以來，北約卻依然存在，更歷經了三次東擴。本文寫作的目的，便欲透過重新檢視國際關係理論三大主要學派的觀點，對於後冷戰時期的北約存續提出解釋。 在現實主義學者陣營中，摩根索與華爾滋的「權力平衡」論點與北約發展的史實不符；施韋勒的「扈從利益」論點僅部分解釋了國家聯盟行為，對於「扈從」概念的界定又出現前後不一；米爾斯海默的「推卸責任」論點試圖同時涵蓋「制衡」與「不制衡」兩種選項，而純粹的「推卸責任」策略又必須依賴其他國家願意承擔，因此不易成功。瓦特的「威脅平衡」理論雖仍有不足之處，但較適合解釋本文的個案。筆者認為，後冷戰時期的北約便是面臨了大規模毀滅性武器擴散、俄羅斯存在與恐怖主義等威脅，才強化了盟國繼續合作的意願。 從新自由主義學者的觀點而言，國家若欲在無政府狀態的國際體系中維持合作關係，便需要以互惠為基礎而運作的國際制度。當國際制度能隨著成員的需求而調整時，就能獲得更多支持。由於美國的優勢國力受到北約的制度規範與集體決策機制削弱，又具有軟權力的勸服力量，遂吸引了中、東歐國家加入聯盟。此外，民主國家之間較不容易發生戰爭。這些因素都維繫了北約盟國在後冷戰時期的合作關係。 由於後冷戰時期的北約在訴求「內群體」偏袒的同時，卻未激化「外群體」歧視。建構主義學者認為，若隨著聯盟關係的發展，成員之間能培養出休戚與共的集體身份，將個別的國家安全問題視同為集體的安全議題時，彼此便超越了傳統軍事聯盟在攻擊與防禦上合作的功能，而達到安全共同體的境界。北約所具備的規範特性也進一步增強了其對盟國的型塑能力。 聯盟的本質在於合作。但關鍵是國家為何合作、如何促進合作，以及如何決定合作對象或競爭對手。事實上，後冷戰時期的北約並未放棄對付共同威脅的核心目標，卻也逐漸發展出安全管理的功能，不但參與了維和行動，也建立起和俄羅斯與烏克蘭的對話機制，更凝聚了盟國的信念而形成具有集體身份的安全共同體。 / In the aftermath of WWII, North Atlantic Treaty Organization (NATO), mainly led by the U.S., was formed to deter U.S.S.R.’s aggression. This organization signified the bipolar system of international relations. When the Cold War came to an end, many scholars once predicted NATO would collapse. However, the alliance still endures for decades and enlarges eastward three times. The purpose of the dissertation is to reappraise the perspectives from three major schools of International Relation theory and provide some explanation of NATO’s endurance in the post-Cold War era. In the camp of realists, the balance-of-power theory raised by Hans J. Morgenthau and Kenneth N. Waltz is inconsistent with the facts of NATO’s development. The bandwagon-for-profit theory proposed by Randall L. Schweller only gives partial explanation of international alliances and takes a contradictory position on the concept of bandwagon. The buck-passing theory maintained by John J. Mearsheimer tries to include both the options of balance and not-balance on the one hand, while depends heavily on other states’ willingness to take the responsibility of balance on the other hand. As far as we know, the latter seldom results in success. Although the balance-of-threat theory sustained by Stephen M. Walt still has some shortcomings, it can provide a better explanation of the case discussed in the dissertation. This author concludes that NATO faces multiple threats of the spread of WMD, the existence of Russia and transnational terrorism in the post-Cold War era. That’s why the allies continue to cooperate. From the standing points of neo-liberalists, if states want to maintain cooperation under the anarchical international system, they will need international institutions based on reciprocity. When international institutions can be adjusted with the demand of their member states, they will obtain more supports. Because the primacy of the U.S. was reduced by the institutional rules and joint decision making process in NATO and accompanied with persuasive soft power, some Central and Eastern European Countries (CEEC) were drew to join the alliance. Moreover, there are few wars among democracies. For all these reasons, NATO still survives until now. When NATO seeks to develop in-group favoritism in the post-Cold War era, it does not activate out-group discrimination. Constructivists state that if members of alliances can cultivate their collective identities and transform national security problems into collective ones, they can go beyond traditional military alliances and become security communities. Features of norms in NATO also strengthen their capabilities in shaping the alliance. The essence of alliance is cooperation. Its key points for states lie in why they cooperate, how to facilitate their cooperation and how to choose their partners or opponents. As a matter of fact, in the aftermath of the Cold War, NATO doesn’t give up its core purpose of fighting against common threats, while it develops the function of security management gradually. Besides, NATO takes part in the peace-keeping operations and builds the mechanisms for communication with Russia and Ukraine. In the end, NATO solidates the belief from its member states and turns into a security community of collective identity.