How did presidents Eisenhower Kennedy and Johnson begin or change the role played by the US in the Vietnam War?

Presidents Eisenhower, Kennedy and Johnson each altered the United States' role in the Vietnam War. Eisenhower entered the US into the Vietnam War in an effort of heroism. Eisenhower believed in the Domino Theory, which was that if one nation fell to Communism others would fall too. Eisenhower's had rollback policies aka the removal of Communism in areas that were already Communist. The war on Communism wasn't completely popular in the US so Eisenhower's concern that the loss of Vietnam would eventually lead to the loss of Japan and he might become unpopularity with citizens for "losing Vietnam" was valid.

Kennedy worked to contain Communism. Like Eisenhower, Kennedy supported the Truman Doctrine. He attempted to contain Communism by sending more troops and "green berets". Kennedy also authorized the spraying of chemicals to kill foliage making the enemy easier to find and defeat. Kennedy supported the overthrow of Diem and shortly after Diem's death, Kennedy was assassinated.

Johnson believed in calibrated escalation of the war. One tactic he used was bombing specific targets in North Vietnam to get authorities to comply. He also got congress's permission to take all necessary measures to win the war. Though things weren't going as planned, he worked to convince Americans that we were winning the war. Each President, Eisenhower Kennedy and Johnson, involved the US in different roles in the Vietnam War.