- Vietnam : A country in Southeast Asia, neighboring China, Laos, and Cambodia, and with seacoast on the Gulf of Thailand, Gulf of Tonkin, and South China Sea. Now the unified Socialist Republic of Vietnam, under a Communist government with a market economic system, it spawned from ancient kingdoms, was a colony called French Indochina, and was partitioned into the Democratic Republic of Vietnam (North Vietnam) and Republic of Vietnam (South Vietnam) between 1954 and 1975.
- Cochin China : In French Indochina, the southernmost part of Vietnam, including the Mekong Delta; roughly corresponded to IV Corps tactical zone of the Republic of Vietnam
- Tonkin : The northernmost part of Vietnam, located on the fertile delta of the Red River.
- II Corps tactical zone : The geographical command of the Army of the Republic of Viet Nam that covered more land mass than any other region, in Central Vietnam including the Highlands. It roughly corresponded with the operational area of the U.S. II Field Force Vietnam.