In September 1940, just months after France capitulated to Germany, Japanese troops took advantage of French weakness to station troops in northern Vietnam for the purpose of cutting off the supply route to the southern flank of the China Theatre. From 1940 to March 1945, the French retained their administrative responsibilities, police duties, and even their colonial army in exchange for allowing Japanese troops and material to pass through Indochina. By 1943, however, there were signs that the Japanese might lose the war. The United States had begun the island-hopping sweep through the South Pacific. A seaborne Allied landing in Indochina and an overland attack from China became real threats to the Japanese. In addition, an upsurge of Gaullist sentiment in Indochina after Charles de Gaulle returned to Paris at the head of the French Provisional Government in September 1944 added to Japanese concerns.
