日本安保政策演進之分析（2012~2025）

Abstract

自2012年12月安倍晉三第二次內閣成立以來，至2025年10月的十餘年間，日本的安全保障政策經歷冷戰結束以來最具意義的演進。從成立國家安全保障會議、制定首份《國家安全保障戰略》、解禁部分集體自衛權，到2022年岸田內閣通過「安保三文書」並保有「反擊能力」，日本正逐漸轉向尋求更具自主性與能動性的防衛姿態。本研究旨在探討驅動此一演變的核心動因，採用層次分析法（Level of Analysis），分別從「國際體系」、「國內政治」與「個人決策」三個層次，系統性剖析日本安保政策演進的內在邏輯。 在國際層次方面，本研究發現外部威脅的變化是驅動日本安保政策轉型的根本動力。隨著美中戰略競爭格局的成形，以及中國在東海、南海及臺灣海峽展現出的修正主義意圖與「灰色地帶」脅迫，日本將中國的定位從「擔憂事項」升級為「前所未有的最大戰略挑戰」。此外，北韓核導彈技術的突飛猛進，以及2022年2月俄羅斯入侵烏克蘭後導致更加激化的地緣政治態勢，強化日本安保政策之危機感，促使其必須透過強化美日同盟、推動「自由開放的印度太平洋」（FOIP）願景，以及加強與北約、澳、英、菲等理念相近國家的合作，以構建多層次的嚇阻網絡。 在國內層次方面，1990年代以來的統治機構改革確立「官邸主導」的決策體制，削弱傳統官僚與派閥的主導權，使首相能更有效地貫徹安保議程。然而，國內政治仍發揮著過濾與制約的作用。作為執政聯盟夥伴的公明黨，在集體自衛權行使範圍與防衛裝備移轉等關鍵議題上扮演「踩煞車」的角色。在野黨則透過國會議事運作，迫使執政黨在立法過程中做出妥協。同時，少子高齡化帶來的人力資源短缺與財政壓力，以及民意對修憲與防衛增稅的保留態度，亦對安保政策的推進速度與幅度構成一定程度的限制。 在個人層次方面，領導者的信念與意志扮演關鍵的催化劑角色。安倍晉三承襲岸信介的政治遺志，致力於「脫離戰後體制」，其強烈的歷史使命感奠定安保改革的基石。菅義偉與岸田文雄雖風格各異，但在日益嚴峻的安保環境下，基本延續並深化安倍路線。特別是出身廣島的岸田文雄，雖具宏池會的鴿派傳統，但在俄烏戰爭衝擊下，展現推動防衛費提升與保有反擊能力的決斷力。石破茂則基於其對防衛事務的深厚興趣，力求美日同盟關係的對等化。 本研究結論指出，2012年至2025年日本安保政策的演進，是國際體系壓力、國內政治折衝與領導者意志三者動態交織的結果。其中，來自中國等外部威脅的國際層次因素提供最主要的驅動力，國內制度與民意劃定政策變革的邊界，而政治領袖的決策則引導具體的實踐路徑。日本正朝向一個在強化美日同盟，與具備更高戰略自主性的道路邁進。

Since the inauguration of the second Abe Shinzo administration in December 2012, through October 2025, Japan's security policy has undergone its most significant evolution since the end of the Cold War. From the establishment of the National Security Council (NSC), the formulation of the first "National Security Strategy," and the partial lifting of the ban on the right of collective self-defense, to the adoption of the "Three Security Documents" and the acquisition of "counterstrike capabilities" by the Kishida administration in 2022, Japan is gradually shifting towards a defense posture characterized by greater autonomy and proactivity. This thesis aims to explore the core drivers behind this evolution. Utilizing the Level of Analysis framework, this study systematically examines the internal logic of Japan's security policy evolution from three distinct levels: systemic, state, and individual level. At the systemic level, this study finds that shifts in external threats constitute the fundamental driving force behind Japan's policy transformation. With the crystallization of US-China strategic competition and China's display of revisionist intent and "gray zone" coercion in the East China Sea, South China Sea, and Taiwan Strait, Japan has elevated its definition of China from a "an issue of concern" to an "an unprecedented and the greatest strategic challenge." Furthermore, the rapid advancement of North Korea's nuclear and missile technologies, coupled with the intensified geopolitical tensions following Russia's invasion of Ukraine in February 2022, has reinforced Japan's sense of crisis regarding its security policy. Consequently, Japan has been compelled to strengthen the Japan-US alliance, promote the "Free and Open Indo-Pacific" (FOIP) vision, and deepen cooperation with like-minded partners such as NATO, Australia, the UK, and the Philippines to construct a multi-layered deterrence network. At the state level, governance reforms since the 1990s have established a "Kantei-led" (Prime Minister’s Office-led) decision-making system, diminishing the traditional dominance of bureaucrats and factions, thereby enabling the Prime Minister to implement security agendas more effectively. However, domestic politics continues to act as a filter and constraint. Komeito, the junior coalition partner, has played a "braking" role on critical issues such as the scope of exercising the right of collective self-defense and the transfer of defense equipment. Opposition parties have also forced compromises from the ruling party during the legislative process through parliamentary maneuvers. Concurrently, labor shortages and fiscal pressures resulting from a declining birthrate and aging population, along with public reservation regarding constitutional revision and tax hikes for defense spending, have imposed substantive limits on the pace and scope of policy advancement. At the individual level, the beliefs and will of political leaders have served as crucial catalysts. Shinzo Abe, inheriting the political legacy of Nobusuke Kishi, was driven by a strong historical mission to "break away from the postwar regime," laying the foundation for security reforms. His successors, Yoshihide Suga and Fumio Kishida, despite differing leadership styles, largely continued and deepened the Abe line amidst an increasingly severe security environment. Notably, Kishida, despite his dovish Kochikai background and Hiroshima roots, demonstrated decisiveness in increasing defense spending and acquiring counterstrike capabilities in response to the shock of the Ukraine war. Shigeru Ishiba, grounded in his profound interest in defense affairs, has sought to pursue a more equal Japan-US alliance relation. This thesis concludes that the evolution of Japan's security policy from 2012 to 2025 is the result of the dynamic interplay between systemic pressures, domestic political bargaining, and leadership will. Among these, international factors—specifically external threats from actors such as China—provide the primary impetus, while domestic institutions and public opinion delineate the boundaries of reform, and the decisions of political leaders guide the specific trajectory of implementation. Japan is advancing along a path toward a strengthened Japan-US alliance combined with heightened strategic autonomy.