How did the french lose control of vietnam

The French soldiers were not prepared to fight against guerrilla forces.

Explanation:

It will soon be shown that the French army, trained in conventional warfare, was not ready for confrontation with easily moving guerrilla forces. This was especially noticeable in the north of the country where the positions of the colonial army were scattered. The Vietminh practiced concentrated force attacks on French positions, thus destroying position by position. In the event that Vietminh aid was sent to the attacked forces, it would often find out very quickly, and in most cases would be ambushed to kill thousands of colonial soldiers. In October 1950, only one such ambush killed 6,000 colonial soldiers.