Vietnam had to wage a long drawn bloody wars first against France, then against Japan and lastly against the super power the USA in Vietnam. Fear of communism: This always haunted the capitalist USA. The US had resolved to fight against this dragon in any part of the world. When communism raisedits ugly head in Vietnam, the US did not keep quit as a spectator, it jumped into the war fare. French Debacle:US entry into the Vietnam war was the outcome of humilating defeat of the France, a European country, at the hands of a small Asian country Vietnam. Being the leader of the capitalist world, US wanted to teach Vetnam a lesson. Secondly, France was an alloy of the US in Second World War. Violation of Geneva Conference: When the Ho Chi Minh govt, in North Vietnam and National Liberation Front in South Vietnam agreed to unify the two parts, in violation of the Geneva conference, US could not remain as a mute spectator.