The US foreign policy of containment was the main motivation behind the American intervention in Vietnam. This policy of containment was based on the theory of stopping any country from following communism and that was considered a disease by the US. Also the taking over of Vietnam by a military dictator added fuel to fire. Firstly the Americans tried to bring up a local army by training the local people. After that they tried to push in the US army to crush communism as well as the military dictator.