Because of Vichy France’s collaboration with Nazi Germany, Japan’s axis ally in World War II, the Japanese occupied all of colonial Indochina during most of World War II but did not overthrow the French administration. Rather the Japanese allowed Vichy to continue operating the colony and supplying the Japanese war machine in its war in the Pacific. Things changed, however, following the Allied liberation of France in 1944, the disappearance of Vichy, and the shift of the Allied war effort to Asia. Fearful of a possible Allied landing in Indochina and the likely defection of the local French to the enemy camp in such a scenario, at 18H00 on 9 March 1945 the Japanese ambassador to French Indochina presented an ultimatum to the governor general, Admiral Jean Decoux, requiring that the French place all of their military and police forces under Japanese control. The Japanese did not wait for a reply. The army quickly interned most of the French colonial army and administrators, replacing the large majority of them with Vietnamese, Lao, and Khmer. French troops in Tonkin put up stubborn resistance in some areas before being captured, killed, or forced to flee towards the Chinese border. In a matter of days, the Japanese had brought down colonial French Indochina. French treaties were abrogated and nationalists in Laos, Cambodia, and Vietnam declared the independence of their new states, some more sincere about it than others. The effects of the Japanese coup were immense. For one, the rapidity with which the Japanese defeated the French made it clear to Vietnamese nationalists in particular that the French were not invincible. Second, whatever the contradictions, the Japanese took the lid off nationalist aspirations that had been growing rapidly since the 1920s, the winds of which had even been fanned by Vichy and Japan’s competiting patriotic drives. During a secret mission to Hanoi, Paul Mus witnessed the coup with his own eyes as he escaped from the city. He reported to his superiors that the coup had marked the “profound evolution of a mentality which can only be called national”. And of course the overthrow of the French, followed by the defeat of the Japanese in August 1945, created the favourable conditions thanks to which the Viet Minh took power in all of Vietnam’s main power centres during the second half of August 1945. See also AUGUST REVOLUTION; CIVIL WAR; COLLABORATION; DEMOCRATIC REPUBLIC OF VIETNAM; VIET MINH.