1930年代中期的英國，已非18、19世紀的日不落帝國，特別是歷經第一次世界大戰（以下簡稱一戰）的長期消耗，英國疲態漸顯，國力早已不復往昔，海軍戰力上所謂的「兩強標準」，亦已成為過去。因此，一戰後的英國雖然勉強維持著世界一等海權國的顏面，但大規模的軍力削減，還是使得英國在國際事務上的實質影響力逐漸下滑，有時甚至顯得力有未逮。加上又要面對德國勢力在歐洲的復興與挑戰，英國實在無太多餘力，可以兼顧遠東局勢。有限的國力、無法同時因應歐亞變局，以及缺乏強大盟邦奧援的現實條件，迫使英國在華面對日本的強勢挑戰時，不太可能再像過往一般採取強硬態度，或許只能退讓，並透過操作外交上的戰略模糊空間，來與日本虛與委蛇，盡量維持英國在華的利益與體面。本文利用英國外交部檔案（FO371），深入探究1937年淞滬會戰期間，隨著中日軍事衝突進一步擴大，英國政府內部對於遠東局勢發展與中日戰爭狀態的評估分析，以及可能採取的因應之道。其中最為關鍵的，乃是英國外交部嘗試利用中日既未宣戰，也沒有公開宣布進入「戰爭狀態」的現況，籌思從國際法與慣例著手，透過《國際聯盟盟約》（League Covenant）、《九國公約》（Nine Power Treaty）、《非戰公約》（Kellogg-Briand Pact）等國際條約的規範，發掘出可能在法理上反制日本的模糊空間，藉此操作戰略模糊手段，以維護英國既有利益。
By the mid-1930s, Great Britain was no longer the British Empire of the 18th and 19th centuries. After the prolonged devastation of World War I, Britain's national strength had faded, and the so-called "two-power standard" of naval power had become a thing of the past. Therefore, while Britain managed to maintain its prestige as a world-leading maritime power in the post-war era, the massive reduction in its military strength led to a gradual decline in its actual influence in international affairs, sometimes it even appeared to be faltering and inadequate. Furthermore, facing the challenges posed by the resurgence of Germany in Europe, Britain lacked the necessary resources to simultaneously manage the Far East. Limited national strength, inability to manage affairs in both continents, and the lack of strong allies meant that Britain was unlikely to adopt its previous strong stance in handling Japan's aggressive actions in China. It was likely that Britain would have to retreat and opt for a diplomatic strategy of strategic ambiguity, playing both sides with Japan, thereby indirectly maintaining its interests and dignity in China. Drawing on British Foreign Office archives (FO371), this article explores the British government's internal assessments and analyses of the Far East situation and the Sino-Japanese conflict, as well as its potential responses, during the Battle of Shanghai in 1937. Crucially, the Foreign Office sought to exploit the fact that China and Japan had neither declared war on the other nor publicly declared a state of war. It thus explored the ambiguous legal space for countering Japan through international law and conventions, drawing on the norms of international treaties such as the League of Nations Covenant, the Nine-Power Treaty, and the Kellogg-Briand Pact. This approach of strategic ambiguity, Britain hoped, would serve to safeguard Britain's existing interests.
Great Britain, Foreign Office Documents. Foreign Office Files: China, 1919-1980.（《英國外交部解密檔案：中國》）（臺北，中央研究院近代史研究所郭廷以圖書館藏）FO371/20954.
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Great Britain, Foreign Office Documents. Foreign Office Files: China, 1919-1980.（《英國外交部解密檔案：中國》）（臺北，中央研究院近代史研究所郭廷以圖書館藏）FO371/20955.
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Great Britain, Foreign Office Documents. Foreign Office Files: China, 1919-1980.（《英國外交部解密檔案：中國》）（臺北，中央研究院近代史研究所郭廷以圖書館藏）FO371/20976.
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