Japan's occupation of Vietnam during World War II further stirred nationalism. Vietnamese communists under Ho Chi Minh organized a coalition of anti-colonial groups, the Viet Minh, though many anti-communists refused to join. After Japan stripped the French of all power in March 1945, Ho Chi Minh announced the independence of the Democratic Republic of Vietnam on September 2, 1945.

The 1954 Geneva agreement provided for a cease-fire between communist and anti-communist nationalist forces, the temporary division of Vietnam at approximately the 17th parallel, provisional northern (communist) and southern (noncommunist) zone governments, and the evacuation of anti-communist Vietnamese from northern to southern Vietnam. The agreement also called for an election to be held by July 1956 to bring the two provisional zones under a unified government. However, the South Vietnamese Government refused to accept this provision. On October 26, 1955, South Vietnam declared itself the Republic of Vietnam.

After 1954, North Vietnamese communist leaders consolidated their power and instituted a harsh agrarian reform and socialization program. In the late 1950s, they reactivated the network of communist guerrillas that had remained behind in the south. These forces--commonly known as the Viet Cong--aided covertly by the north, started an armed campaign against officials and villagers who refused to support the communist reunification cause.

After reunification, the government confiscated privately owned land and forced citizens into collectivized agricultural practices. Hundreds of thousands of former South Vietnamese Government and military officials, as well as intellectuals previously opposed to the communist cause, were sent to re-education camps to study socialist doctrine.

While Vietnamese leaders thought that reunification of the country and its socialist transformation would be condoned by the international community, this did not happen. Besides international concern over Vietnam's internal practices, the Vietnamese invasion of Cambodia in 1978 and its growing tight alliance with the Soviet Union appeared to confirm suspicions that Vietnam wanted to establish hegemony in Indochina.

Vietnam's invasion of Cambodia also heightened tensions that already existed between Vietnam and China. Beijing, which had long backed the Khmer Rouge regime in Cambodia, retaliated in early 1979 by initiating a border war with Vietnam.

Vietnam's tensions with its neighbors and its stagnant economy contributed to a massive exodus from Vietnam. Fearing persecution, many Chinese in particular fled Vietnam by boat to nearby countries. Later, hundreds of thousands of other Vietnamese nationals fled as well, seeking temporary refuge in camps throughout Southeast Asia.

The continuing grave condition of the economy and the alienation from the international community became focal points of party debate. In 1986, at the Sixth Party Congress, there was an important easing of communist agrarian and commercial policies.