Bao Dai, the leader of the French-recognized faction, also claimed that his party, and not Minh’s, had authority over the country. By 1950, the Truman administration had begun sending American military advisors to Vietnam to support the French. Eventually, the United States began lending financial support to France’s war against Minh supporters. While western nations were outlining such policies as those set forth by the Geneva Convention (1954) and SEATO (1954), internal division within Vietnam continued to escalate. Fearing the threat of the expanse of Communism throughout the Pacific Asian area, the United States, during the Eisenhower and Kennedy administrations, continued aiding the French, until the number of U.S. military personnel deployed to Southeast Asia numbered nearly 20,000. Under the Johnson administration, the U.S. destroyers Maddox and C. Turner Joy received fire from North Vietnamese boats, and President Johnson reacted by ordering an aerial assault of North Vietnam. Only a few days after this incident, Congress passed the Gulf of Tonkin Resolution, which extended to the president the necessary authority to conduct war, though war was never officially declared.

Within months, the first combat-ready unit was deployed to U.S. Marines headquarters at Da Nang in March, 1965. U.S. involvement continued to steadily increase, and by the close of 1967 over a million American troops were in Vietnam, despite the growing sentiment of the American public to stop or withdraw from the war. The undeclared “war” eventually became the United States’ longest foreign policy engagement. After years of intense battle, the United States withdrew the last combat troops from Vietnam in March 1973. More than 1.2 million Americans served in the war; nearly 60,000 died in service.

The objective that the United States supported — in short, preventing Vietnam from becoming a communist foothold — was never realized. In April 1975, Saigon surrendered to the communist revolutionaries; the following year, the Socialist Republic of Vietnam was declared.