Ngo Dinh Diem in The Vietnam War
Ngo Dinh Diem (1901–1963) was a staunchly anticommunist Vietnamese statesman who refused to ally with Ho Chi Minh after the Franco-Vietnamese War. With the support of the United States government, Diem led South Vietnam from 1954 to 1963, when he was assassinated alongside his brother in a military coup.
Named President of South Vietnam in 1954, Ngo Dinh Diem consolidated power in Saigon and sought to expel, imprison, or execute those who opposed his regime. With the support of the United States, he refused to hold countrywide elections in 1956 (a stipulation of the 1954 Geneva Accords), fearing—almost certainly correctly—that he'd lose to Ho Chi Minh.
Diem was a terribly unpopular leader, known for his paranoia and his ruthlessness. Many South Vietnamese grew to resent and fear his repressive policies, which ultimately contributed to the rise of the NLF and the Viet Cong.