Final answer:
The battle of DienBienPhu in 1954 was the decisive battle where the French were defeated by Vietminh forces, leading France to relinquish control over Vietnam and marking a critical moment in Vietnamese independence.
Step-by-step explanation:
The turning point in France's colonial grip on Vietnam occurred in 1954 during the pivotal Battle of DienBienPhu.
This momentous conflict unfolded between the French and HoChiMinh's Vietminh forces, culminating in a definitive defeat for the French after eight years of arduous struggle.
The fall of DienBienPhu served as the catalyst for France's relinquishment of control over Indochina, with Vietnam partitioned into a communist north and a non-communist south.
This significant military setback not only marked Vietnam's stride toward independence but also dealt a severe blow to French colonial dominance in Southeast Asia.
Importantly, it set the stage for subsequent United States involvement in Vietnam, shaping the course of one of the most consequential conflicts in the 20th century.