2014 年 2 月爆發的烏克蘭危機是歐洲當前最嚴肅的區域安全挑戰，這不僅是因為烏克蘭危機使得歐洲再度出現區域衝突情勢，同時也因列強介入而使得地緣競爭強度漸趨激烈。學界多探討烏克蘭危機及其背後的歐洲地緣競爭意涵，然較少從烏克蘭內部安全策略選擇的角度分析，本文嘗試補充此等觀點，從內部因素出發，分析烏克蘭內部政治如何影響區域危機的發生。

本文認為:第一，烏克蘭受制於強權競爭，使烏克蘭與其他中間地帶國家，都必須在左右強權互動格局下進行回應與策略選擇，不過烏克蘭內在特殊性有別於其他國家，這個特殊性是政策變異程度高、策略選擇極端化，而解釋這個極端現象有賴內部因素分析方式，才能一窺全貌。第二，本文內部因素理解方式乃是透過決策者、社會結構與憲政制度著手，解釋烏克蘭安全政策變動之因，本文發現決策者因素與安全政策變動關連並不明顯，分裂型社會因素才是重要關鍵，憲政制度則是回應分裂型社會結構下，政治權力游移的展現。第三，烏克蘭策略選擇呈現出規律的擺盪模式，此種擺盪未隨時間遞移而漸趨緩和，相對的，擺盪還因為歐俄強權介入而使衝突情勢漸次升高，這顯示強權環伺下中間地帶國家的無奈。最後，本文指出烏克蘭失去克里米亞、盧甘斯克、頓內茲克等地後，烏克蘭社會結構將受到重新調整，擺盪模式或可能受到衝擊，安全策略也可能因而有調整。

Ukraine is situated strategically between EU and Russia. The outbreak of the Euromaidan Revolution(February 2014)designates the advent of severe geopolitical competition in the European continent. Though it is crucial to understand this competition through the lens of great power rivalry, small and medium countries that exert certain leverages between great powers also warrant our attention. We argue that the domestic approach is suitable to explain the transformation of Ukraine’s security choices. We first develop an analytical framework that delineates the importance of domestic perspective in analyzing the Ukraine crisis, then examine the formation of Ukraine’s security policies and scrutinize her domestic approach consisted of political elites, divided society, and constitutional development factors. We also employ an explanatory pendulum model to analyze the shifts of Ukraine’s security choices; some theoretical implications are drawn from the discussions.