The French ruled Vietnam but allowed the emperors to remain as a figurehead. He ruled the country as far as when things interfered with the French, then he was censored. He was effectively a puppet of the French.
The French's police force was called 'gendarmerie'.
Bao Dai was Vietnams last emperor he cooperated with the French and became a Francophile - accepted the French culture.
The French were in Vietnam to exploit human and natural resources. The French educated and setup French schools for the Vietnamese. The Vietnamese who collaborated with the French were called 'nguoi phan quoc' (traitors) Boa Dai could never escape this label.
The French heavily exploited the land of alcohol, salt, opium and rice and used Vietnamese to harvest it all (they were known as 'coolies')
Ho Chi Minh, born in 1890, lead a revolution against the French. He was primarily a nationalist but later saw communism as a way to free his people from French grip.
Ho studied in Russia and France and joined communist parties. He later setup Indochinese Communist Party (ICP) in 1930.
The Japanese took over Vietnam in 1940. French were allowed to stay but did not have any power at all. The Japanese had control from 1940-1945.
In 1941, Ho created the Viet Minh which was a new revolutionary movement and had many branches, one of which was a military wing. Ho stressed that every Vietnamese person, regardless of ages, sex... was vital to the success of the revolution.
Ho's propaganda teams built up huge support and these people became the People Army. In 1945, the Japanese left Vietnam. I 1945, Ho met with Americas CIA. They made an agreement that the US would train them and the Vietminh would try locate shot down pilots and gather intelligence...