Ngo Dinh Diem was a Vietnamese politician who served as the first president of South Vietnam from 1955 until his assassination in 1963. He was a staunch anti-communist and was initially supported by the United States in the early stages of the Vietnam War. His rule became increasingly authoritarian and nepotistic, leading to widespread discontent, particularly among the Buddhist majority. Diem was ultimately overthrown and killed in a military coup, a pivotal event that deepened American involvement in Vietnam.