Ngo Dinh Diem: He was the first president of South Vietnam who faced challenges due to corruption within his government and opposition from communist forces.
Viet Cong: Also known as National Liberation Front (NLF), they were communist guerrilla fighters based in South Vietnam who aimed to overthrow the South Vietnamese government.
Domino Theory: This theory suggested that if one country fell to communism, neighboring countries would also follow suit like a row of dominos. It was often used to justify U.S. involvement in Vietnam.