The same thing that caused every other war. Greed. The North tried to take over the South, the South asked the USA for help and it escalated from there. Or that's my understanding of it. Anyone got a more detailed answer please.

During World War II the Japanese conquered French Indochina as Vietnam was called at the time. After the defeat of Japan the French tried to reimpose French rule but the people of Indochina now no longer would accept rule by a foreign power. So the French tried to reimpose their rule but were defeated by the Vietnamese and so in the peace negotiations Vietnam was divided into a Communist North Vietnam and an independent South Vietnam under western influence. The communist North then tried to reunite the country as a communist country and the Non-Communist south tried with French help at first and then later with American help to retain its independence. The American military presence steadily increased till at its height it was over 500,000 men. Even so victory was elusive as the Communist had adopted guerrilla tactics and avoided direct confrontations and trying to "hold territory" but attacked at its will and "controlled" large areas of the country. As in Iraq the Americans could "take" any territory but then the Vietnamese would attack them at will and then fade back into the countryside. America won every battle but the Communist would not quit and after years and years and years of war the Americans made a cosmetic treaty which would allow them to withdraw and left the South Vietnamese to their fate. As someone who personally participated I can tell you if we had not given up we still would be fighting those people. They would just not give up and didn't care how many people or years it cost. You have those who say we could have won the war if we had invaded the north but even though we could have defeated the standing army they would have just switched to guerilla tactics and we would have been in the same situation we were in the South. Those people would just not give up.

I agree with Marcus accept on a few details. The communist North didn't just try to reunite the country as communist for no reason. At the Geneva agreements it was agreed for there to be free elections held in 1956, so that the people could decide if they wanted to be communist or capatalist. However, the capatalist leader Diem was extremally harsh and unpopular, by the time the 1956 elections came around, the majority of the South Vietnamese population wanted to be communist. In order to stop this from happening, the USA, under President Eisenhower, rigged the election - remember this was the time of the red scare. (Very hypocritical as Eisenhower had been accusing Stalin of rigging the elections in Eastern Europe) We know it was rigged because Diem recieved 605,000 votes even though there were only 450,000 voters!

China! Mr Bill

When Vietnam was finally granted independance by the French government, the country was divided by two leaders, on Communist, on Capitalist. The communist leader was Ho Chi Mihn. The capitalist leader was Ngo Diem Dihn. When they couldn't agree on how the government was to be won, the world stepped in and basically set up a conference between everyone and set up Vietnam to divide in half for 2 years, the North lead by Ho Chi Mihn, the south lead by Ngo Diem Dihn. After those two years, the people of Vietnam would vote for the type of government they wanted, the South leader knew he was going to lose, so decided to stop going by the rules and started a war.

A lot of things led up to the start of the war, but you can thank JFK for really getting it going. JFK in a briefing with his intel folks, mentioned that the S. Vietnamese needed a coup. The Intel folks thought he was giving the GO for them to arrange it. When they did, it caused a spiraling instability ever since. The S. Vietnamese president it turns out was the only thing really holding things together. Below is the link to hear JFK talk about his blunder. http://tapes.millercenter.virginia.edu/clips/1963_1104_jfk_vietnam_memoir.swf.

not us

route are in the japanese occupation of indo china but the spark was the gulf of tonkin incodent when three VC P-4 torpedo boats attacked the USS Maddox

Hubris

http://www.pbs.org/battlefieldvietnam/history/index.html

Does anybody, other than the master planners, really know? I'm sure that 100 years from now, the Iraq war will probably be thought off as a response to 9/11 - Ha ha ha!

The US was afraid that if Communism got a foot hold in Asia, there would be a domino effect whereas many other countries would "go" communist such as China. There was an overwhelming fear of that the whole eastern hemisphere would turn against the US eventually.