Vietnam is about 9000 miles away from the USA, but what provoked the USA to determine to get involved in the civil war between the Vietnamese back in the 40's-70's far away from them? Why did they intervene in the Vietnam War between 1954 and 1963? Actually, the answer is very simple. They were afraid of the spreading of the communism and wanted to stop it before it was too late.
Militarily, following up by the defeat of French, the French was compelled to leave Vietnam which would leave a power void for Ho Chi Minh, a communist, to take over easily. In the Battle of Dien Bien Phu, 1954, 16,000 French troops were either killed or captured by the Viet Minh. It convinced the French government to leave Indochina as soon as possible. It was like handed the part of Vietnam which was under French's control to Communism, and the US would not allow it because of the Truman Doctrine--Containment.
Also, the US was heavily involved in the French military financially, even the Viet Minh Supreme Commander, General Vo Nguyen Giap said during a interview in 1996, "We see the Dien Bien Phu victory as the victory [over] the French army and [over] the intervention of the Americans --because in the Dien Bien Phu campaign, 80 percent of the war expenditures were spent by the Americans...So the Dien Bien Phu defeat was a defeat for both the French and the Americans...When we received news of the Dien Bien Phu victory, everyone practically jumped up in the air, they were so happy about it." For both of the sake of containment and honor, the US intervened in that Civil War in 1954.
Internationally, the USA was very unhappy with the Geneva Agreement of 1954. It declared the ceasefire between...