The War in Vietnam America became increasingly involved in the war in Vietnam, mainly because of the domino theory, the fear of the spread of communism. If South Vietnam fell to the communist the US feared that communism would spread throughout Asia and to neighbouring countries. The influence of the previous presidents also caused another main reason for the US to become more involved in Vietnam. But there is one underlining fact; if the ‘French had not left, America would not have become involved in Vietnam at all. There are many more reasons for America to increase involvement in Vietnam, and all of these can be listed in long and short-term reasons, such as Domino theory being long term and Gulf of Tonkin being short term. Some of the reasons have higher influence in the increase in involvement in Vietnam, while others being less important (for example the Gulf of Tonkin incident). The most important factor for America’s involvement was the Domino Theory, conceived by President Eisenhower, which was originally President Truman’s Theory of Containment (Theory evolving into Domino Theory).The theory of containment was the idea of not actually stopping communism but containing it within a country to stop communism from spreading. This theory was used in the Korean War( 1950-53) and had succeeded in containing communism in North Korea. Eisenhower’s theory, the Domino Theory, initially evolved from Truman’s Theory of Containment. Domino Theory was the idea of the spread of communism, which was compared with the falling of dominos, “you have a row of dominos set up you knock over the first and what happens to the last is a cer... ... middle of paper ... ...o the failings of the corrupt Diem, leading to the cancelling of the elections, which angered the North, who retaliated by attacking the south, and in response the Americans increased it’s troops to try meet the threats of the Vietcong and Communism. But some factors can be linked to other factors, domino theory and influence of the presidents. Also some of the Factors are more important than others, the most important being the Domino Theory, and the French Exit, but the UN not being as important in the reasons why America got more involved. The Domino theory was the justification for the war. The Gulf of Tonkin was only an excuse , French exit was the void that America filled, and Diem’s failings, all of which linked to the Domino Theory, which is basically the reason why America got increasingly involved in Vietnam.