 In the First Indochina War (1946–1954), the Việt Minh led by Ho Chi Minh defeated the French re-establishment of European colonialism in Vietnam.To fill the geopolitical power vacuum caused by French defeat in southeast Asia, the United States then became the Western power supporting the client-state Republic of Vietnam (1955–1975) headed by Ngo Dinh Diem.Despite possessing military superiority, the United States failed to safeguard South Vietnam from the guerrilla warfare of the Viet Cong sponsored by North Vietnam.