The American ally in South Vietnam whose repressive regime fueled Viet Cong resistance and required more American military aid; he was killed in a coup in 1963.

• A. Ngo Dinh Diem
• B. Ho Chi Minh
• C. Dien Bien Phu
• D. Nguyen Cao Ky

Answer: (A)

The key idea here is identifying the South Vietnamese leader whose authoritarian rule helped drive Viet Cong resistance and thus drew more American military aid, and who was killed in a 1963 coup.

Ngo Dinh Diem led South Vietnam from 1955 until his assassination during a November 1963 coup. His regime was increasingly authoritarian and mirrored in its political repression and religious discrimination, notably toward Buddhists. This repression alienated a broad swath of South Vietnamese society and undermined popular legitimacy, which the Viet Cong exploited by portraying themselves as defenders of national independence against an oppressive regime. As instability grew and U.S. concern about the viability of the Diem government increased, American leaders supported efforts to bolster the regime with more military aid and political backing to counter the insurgency. The coup in 1963—carried out by South Vietnamese military leaders—ended Diem’s rule and removed him from power, illustrating how U.S. involvement hinged on a fragile ally whose repressive tactics ultimately fueled opposition.

Ho Chi Minh was the communist leader of North Vietnam, not an American ally in the South. Dien Bien Phu was a major battle that ended French rule in Indochina, not a person. Nguyen Cao Ky emerged as a South Vietnamese leader after 1963 and was not killed in that year.