Ngo Dinh Diem (1901 - 1963)South Vietnam President. Served as President of the Republic of South Vietnam from Oct 1956 until Nov 1963. He was overthrown by a coup. After the generals had promised Diem that he would be allowed to leave the country they changed their mind and killed him. He was replaced by Nguyen Van Thieu, the chief of staff of the Armed Forces of South Vietnam.