A parcel bomb sent by Ngô Đình Nhu, younger brother and chief adviser of South Vietnamese President Ngô Đình Diệm, fails to kill King Norodom Sihanouk of Cambodia.

A letter bomb is an explosive device sent via the postal service, and designed with the intention to injure or kill the recipient when opened. They have been used in terrorist attacks such as those of the Unabomber. Some countries have agencies whose duties include the interdiction of letter bombs and the investigation of letter bombings. The letter bomb may have been in use for nearly as long as the common postal service has been in existence, as far back as 1764.

James (Giacôbê) Ngô Đình Nhu was a Vietnamese archivist and politician. He was the younger brother and State Counsellor of South Vietnam's first president, Ngô Đình Diệm. Although he held no formal executive position, he wielded immense unofficial power, exercising personal command of both the ARVN Special Forces and the Cần Lao political apparatus which served as the regime's de facto secret police.

South Vietnam, officially the Republic of Vietnam, was a country in Southeast Asia that existed from 1955 to 1975. It first garnered international recognition in 1949 as the associated State of Vietnam within the French Union, with its capital at Saigon. Since 1950, it was a member of the Western Bloc during the Cold War. Following the 1954 partition of Vietnam, it became known as South Vietnam and was established as a republic in 1955. South Vietnam was bordered by North Vietnam to the north, Laos to the northwest, Cambodia to the southwest, and Thailand across the Gulf of Thailand to the southwest. Its sovereignty was recognized by the United States and 87 other nations, though it failed to gain admission into the United Nations as a result of a Soviet veto in 1957. It was succeeded by the Republic of South Vietnam in 1975. In 1976, the Republic of South Vietnam and North Vietnam merged to form the Socialist Republic of Vietnam.

Ngô Đình Diệm was a South Vietnamese politician who was the final prime minister of the State of Vietnam (1954–1955) and later the first president of South Vietnam from 1955 until his capture and assassination during the CIA-backed 1963 coup d'état.