本文主旨在探討 1931 年「九一八」事變之後，至 1937 年「七七」事變爆發，中日關係下的「蘇聯因素」，以及國民政府相關的決策過程。由於日軍侵華相當重要的考量，即為日後「北進」之準備，故「日蘇先戰」曾是蔣中正衷心之期待。直到最後兩年 (1935-1937)，中國實際已入對日備戰階段；在此考量下，蔣開始推動與蘇聯的條約及軍事關係，從而有國共和解之嘗試。迨 1936 年「西安事變」落幕，中蘇、國共合作水到渠成，中國對日更大規模的「戰爭邊緣」冒險，遂於翌年 7 月發動，終至「中日先戰」的結局。因此本文焦點，係集中在南京政府對於「日蘇先戰」的評估，及與蘇聯方面的交涉過程，兼及此過程與中日關係間，競合消長的「列強連環性」。筆者主要引用國史館所藏《蔣中正總統檔案》，對此關鍵時期，中國方面有關日、蘇兩國的和戰決策，嘗試進行一總體性的考察。

This article examines changes in the relations between Nationalist China, the Soviet Union, and Japan after 1931. In particular, it analyzes the Nationalist Government's response to the dilemma posed by there changers. Japan's strategy was to invade China in preparation for World War II. Hence, how to avoid becoming the first sacrifice in the war was foremost in the minds of Chinese leaders, including Chiang Kai-shek (蔣介石). China recognized the necessity of preparing for war in 1935 to 1937, so Chiang started to promote military cooperation with the Soviet Union and making a treaty. Therefore, China and the Soviet Union signed the Sino-Soviet Non-Aggression Pact in 1937 as a result of this cooperation.