The Iraq War. The North Korea Nuclear Crisis. Once Vietnam ...
I grew up after the War of American in Vietnam! The war lasted for 20 years (1953-1975) but came to the end in very short time. American indeed devoted to the freedom of the South Vietnamese, with two big air-strikes to the North, one on the Johnson's administration and another on the Nixon's. They couldn't go beyond the conflict because of the Cold War. American withdrew from the war in 1973 and two years later the South Vietnam Government was fallen. One important detail that resulted to end the war peacefully was the resignation of the South Vietnam President Thieu. It's still on judgement. He was a general and in power since 1963. As the North violated the Peace Accord of 1973 to launch big offensives over the South, he ordered to withdraw the army from a strategic area in the Central with a hope of the American's return. The result was so devastated. He was forced to resign. A few days later, the new government surrendered. He opposed to the American by choosing to refuge in Taiwan, then England, and recently back to the United States.
The North Vietnamese still had bad memoirs about the rule of the Colonial French; therefore, they wanted to free the South. In the 1970s, the Communist Soviet was at peak of the achievements, even in economics the members of the Soviet Block were well in their trades, while American was in troubles for many years. Moreover, American had withdrawn since 1973. With those advantages, in 1975 the North succeeded in launching the war to unite with the South by force. They was so passion with their victory and believed in their idealism. They put all persons worked for the South Vietnam Government in prison. The children of these persons couldn't be allowed to have a higher education (college). They even asked for a big compensation as President Jimmy Carter wanted to establish a normal relationship (waited until 1994!).
The North's strength on military was no question. They defeated the Colonial French in 1954, overthrew the Communist Khmer Rouge- a bloody genocide regime in Cambodia, backed by Chinese in 1978, and won the war against Chinese in the northern border in 1979.
American dropped the war in Vietnam as a strategy. It still had other two fronts: at Germany and at Korea. "We fight for our lives, but with American it's a dark page in its history", said Bui-Diem, a South Vietnam ambassador. As the communism in Eastern Europe and Soviet Union failed in 1990, and Germany united in 1989, the U.S. government allowed all former South Vietnam officers and their families immigrating to the United States.
Reference
Vietnam: A History, by Stanley Karnow (May 1997)