本文討論中日戰爭初期的中法外交關係，以中方進口軍火物資假道越南輸入問題，與法方因應日本抗議而扣押軍火、禁運物資所衍生的三方交涉為主。法屬越南在中日戰爭初期扮演了中國賴以生存之少數交通孔道的重要角色，也成為中、法、日三國交涉與衝突的一個場域。 中日戰爭爆發以後，日軍迅速控制中國沿海區域，目的在切斷所有外援物資管道。國民政府為求突破封鎖，欲假道越南轉運軍火物資來華，訓令駐法大使與法交涉。法國因歐洲局勢緊張，無力東顧，加以日本多次抗議，恐日本藉口侵佔越南，故曾禁止軍火假道內運。但為保全其殖民地計，法國曾與中方洽商軍事合作，以防日軍進佔海南島、入侵越南。蔣介石亦派多方代表赴法交涉，期能就武器供給、假道運輸、派遣軍事顧問三事一併解決。到1939年1月，法方始同意派遣軍事顧問團來華。至9月，歐洲局勢日益緊張，法國又起變化，不准軍事物資轉運，並召回其在華之軍事顧問團。 法國於1940年6月對德投降，維琪政權繼而成立。日方施壓，使越南自6月20日起停止一切物資輸華。至9月間，法、日簽訂軍事合作協定，日軍遂得以進入北圻。1941年7月，日軍又進佔南圻，法屬越南實際已成日軍「南進」之跳板。 戰時中法外交反覆曲折，重慶政府極力要維持西南的補給線，而法國除考慮歐洲局勢外，主要在於確保其印度支那殖民地的主權。對日本妥協讓步，對中國敷衍，使得中法交涉曲折多變。而法國對日妥協的態度，也是戰後失去越南的根源。

　　　　　This article analyses a complicated episode in Sino-French relations during the first phase of the Sino-Japanese War (1937-1945). By using as-yet unexploited documents in China and France, it explains how China imported military materiel via Vietnam, the reactions of France in the face of the protests of Japan, and the negotiations about the imposition an embargo between China and France. After the outbreak of the Sino-Japanese War, Japan soon controlled all the coastal areas of Vietnam in an attempt to cut off the supplies of any provisions to China, as the National Government had used Vietnam as transit for obtaining military materiel. Under the pressure of Japan and fearing threats to its suzerainty over the colony, the French authorities in Vietnam sometimes had to interdict the passage of such goods. But France also tried to make a military cooperation deal with China, to which Chiang Kai-shek responded by sending his commissionaires to Paris to try to resolve three main issues: the provision of military goods, their transit via Vietnam, and a military mission of French consultants to China. In January 1939 France agreed to dispatch a military mission but had to revoke it in September due to the downturn of the situation in Europe. The armistice of June 1940 in France subjected the Vichy government to the Japanese pressure, resulting in the interdiction of goods from Vietnam to China. Moreover, France also signed a military accord with Japan in September enabling Japanese forces to station troops in Tonkin (North Vietnam). By July 1941, the Japanese Army had entered into South Vietnam. In fact, French Indochina became a base of Japan's Southward policy. Sino-French diplomatic relations during the war progressed through three phases: first, China tried hard to maintain its vital supply lines; then, France wanted to keep its suzerainty in Vietnam in the face of Japanese pressures; and finally, Japan overruled the previous two unstable situations. The compromise forced on the Vichy government by Tokyo became a major reason why France lost its all colonies in Indo-China after the War.