Eisenhower's aim was to contain Communism – an ideology that he believed threatened America and, potentially, the rest of the world. Fundamentally, he needed to decide how he was going to stop the expansion of Communism, especially after his predecessor Truman had lost China to Communism. His domino theory suggested that if Vietnam was to fall to Communism, then the surrounding countries one by one, would do so also. This attitude inherently shaped any decisions Eisenhower was to make, some of these providing evidence of sound judgement on his part, such as avoiding direct military involvement. However, other decisions were misinformed, and demonstrate poor judgement, for example Eisenhower actively promoted and supported Diem, even though it was evident he was corrupt.
Even though Eisenhower failed to prevent North Vietnam from becoming Communist, which was never a realistic possibility with the popularity of Ho Chi Minh, he did reject the option of using the atomic bomb on North Vietnam. The use of the atomic bomb on the North would have meant the end of the war, with the South and America victorious. In the 1940s, The Red Scare had created an anti-communist hysteria throughout America, with the belief that Communism could destroy American consumer lifestyles. In order for Cold War relations to remain as they stood, Eisenhower did not take any chances on tensions rising. Although the decision to bypass using atomic weaponry was based on the fear of a nuclear war, rather than on any diagnostic judgement, it did avoid direct involvement with the USSR and China, proving to be a good decision in the course of the Vietnam war.
Although it would have been easy for Eisenhower to simply take over South Vietnam, he made the decision not to. Instead he provided financial aid, especially to the South Vietnamese army, urging them to fight for one another