According to Wikipedia, in 1946 during negotiations between the French and Ho Chi Minh,
One demand by the French was the return to French custody of a number of Japanese military officers (who had been helping the Vietnamese armed forces by training them in the use of weapons of Japanese origin), in order for them to stand trial for war crimes committed during World War II. Ho replied that the Japanese officers were allies and friends whom he could not betray. Then he walked out, to seven more years of war.
Any ideas who these Japanese military officers were, and what were their crimes?