surrounded the French at Dien Bien Phu, a French stronghold for 57 days.
Explanation:
The French decisively lost the First Indochina War in 1954 when Communist fighters for the People's Army of Vietnam "surrounded the French at Dien Bien Phu, a French stronghold for 57 days."
The French surrendered fully and removed their colonial presence on May 7, 1954.
There is also a 1954 Geneva agreement that defines the whole of surrender activities between the two nations.
