Post-War Japanese Security Policies: Analysis based on Defensive Realism with A Case Study on Japanese Nuclear Weapon Policies

本論文旨在研究日本自二次大戰戰後的安全保障政策，並論述較之新現實主義和建構主義，守勢現實主義在解釋日本戰後安保政策上最具有解釋力度。本文首先就歷史的脈絡依序扼要介紹第二次世界大戰之後影響日本安保環境的諸多歷史事件，以及日本在安保政策上的演革。越戰和冷戰無疑在日本的安保政策變革上扮演著重要的角色：前者間接促使日本的自衛隊實力逐步加強，後者則清楚刻畫了對日本威脅之來源的變遷。透過歷史的回顧，不難發現日本雖然和英國同屬海島國家但卻四面楚歌，先有蘇聯大軍壓境，後則有中國與北韓的潛在威脅。其次的研究則發現過往對於日本安保政策與國際關係理論之間關聯之研究仍有不足，且各派國際關係理論所提出之論點多有矛盾之處。據此，本文先就過往依循守勢現實主義對日本安保政策做出研究的學術成果做一介紹與整理，並瞭解到新古典現實主義的出現不但修正了新現實主義，也使守勢現實主義產生了新的變型。考慮到本論文的分析對象為日本此一單一國家，而非整體的國際環境，因此本論文利用新古典現實主義中的守勢現實主義變型：威脅平衡理論和攻守理論來對戰後的日本安保政策進行分析與研究，論證守勢現實主義的解釋力。最後，則運用核武與飛彈防禦政策為例，進行案例的研究與探討。 戰後的日本雖然在憲法上揚棄了擁有發動戰爭的武力，但卻因為韓戰爆發而在美軍的要求下進行再武裝。因應蘇聯日益加強的軍事威脅以及美軍因越戰的陰霾而撤出亞洲的事實，日本在冷戰時期大幅在質與量上增進軍事能力，這點顯然與建構主義的論述有所牴觸。然而，做為經濟超強的日本卻終究沒有背棄與美國的同盟關係，其堅定維護日美同盟的決心使得新現實主義基於權力平衡而做出之「日本必然將會平衡美國」的假設同樣失去說服力。上述兩者乃戰後學界賴以解釋日本安保政策的兩大國際關係理論，卻皆有其論述上的缺陷。相對的，守勢現實主義的威脅平衡理論卻精準地解釋日本在戰後的結盟選擇，也對於日本為何能夠在進行軍事實力的同時避免陷入安全困境之中提出合理論述。 日本的核武與飛彈防禦政策則進一步地證實了守勢現實主義在戰後日本安保政策上的解釋力。日本長期以來受到鄰國的核武恫嚇與威脅：先有冷戰時期的蘇聯，後有積極進行核武現代化的中國與不理性的北韓。然而，日本並未如新現實主義論者所預測地一般獲取獨立的核武實力，也並未完全徹底以道德考量揚棄核武。日本官方文件、官員發言與政策顯然都將威脅納入考量，而以美日同盟做為基礎佈署飛彈防禦系統。 綜論之，透過理論層面的論證以及實際案例的分析，守勢現實主義確然對二次大戰以降的日本安保政策具有解釋力，也因此值得做為未來預測日本安保政策變遷的參考。This thesis intends to study the security policies of Japan since the Second World War, and argue that defensive realism has the strongest explanatory power on these policies, against neo-realism and constructivism. In time sequence, an overview of all the major historical events since WWII that have impacts on the security environment of Japan and the subsequent changes on Japan’s security policies constitutes the first part of the thesis, and points out that both the Vietnam War and the Cold War have played significant roles in shaping Japanese security policies after WWII, with the Vietnam War triggering the consolidation of military power of the Japanese Self-Defense Force and the Cold War marking the change of source of the major threat to Japan. Through the historical review, it is not difficult to find out that Japan has constantly been surrounded by threats, even though it is an island-state like the United Kingdom: first by the Russian forces on its borders, and now with the potential dangers imposed by China and North Korea. The thesis then realizes the insufficiency in the research of the link between international relation theories and Japanese security policies, with emphasis on the contradiction between the viewpoints of the different international relation theories. This thesis then, based on this finding, sorts out the previous research works that use defensive realism to study the security policies of Japan, and at the same time, points out that the emergence of neo-classical realism has created new variants of defensive realism. Understanding the subject of research of this thesis is one single country, Japan, instead of the whole international environment, this thesis makes use of the variants of defensive realism that roots in neo-classical realism, namely balance-of-threat theory and offensive-defensive theory, to study and analyze the security policies of Japan since WWII, and proves the explanatory power of defensive realism. Lastly, Japan’s nuclear and missile defence policies are thoroughly studied as a case study to again prove the explanatory power of defensive realism. Japan surrenders its right to wage war and own a war-fighting military force in its post-war constitution, but the Americans have requested Japan to re-arm under the shadow of the Korean War. In response to the growing military threat from Soviet Russia and the withdrawal of American forces in the aftermath of the Vietnam War, Japan has greatly enhanced its military ability both in quantity and in quality. This certainly contradicts with the contentions of the constructivists. However, being an economical giant, Japan has never abandoned its alliance with the U.S., and its determination in maintaining the alliance has also proven neo-realist’s “Japan to balance the U.S.” hypothesis to be flawed. These two are the two most commonly applied international relation theories in explaining the post-WWII Japanese security policies, yet their arguments are both inperfect. In comparison, however, balance-of-threat theory of the defensive realism school accurately explains Japan’s preference in post-war alliance formation, while the offensive-defensive theory explains why Japan may develop its military capability and yet avoid to be trapped in a security dilemma. The Japanese policy on nuclear weapons and missile defense further proves the explanatory power of defensive realism on the post-WWII security policies of Japan. Japan has long been under nuclear threats from its neighbors: first with the Soviet Union during the Cold War, and later with a quickly modernizing China and the irrational North Korea. Yet, Japan has not developed an independent nuclear force, as predicted by neo-realists, not has it totally abandoned nuclear weapons based on moral grounds, as advocated by many constructivists. Official documents, public statements by government officials and official policies have obviously include “threat” as a factor of consideration, and disposed missile defence systems in accordance to the U.S.-Japan alliance. In short, supported by the results from the discussion of the different international relation theories and the analysis of the case study, defensive realism truly has a strong explanatory power towards the post-WWII security policies of Japan, and can be a convincing reference in predicting future Japanese security policies