The period from 1949 to 1955 in Vietnam, particularly the era of the State of Vietnam and the First Republic of Vietnam, marked a crucial chapter in the historical context of the Indochina War and the dynamic political shifts in the region.

Commencing in 1949, the State of Vietnam was established under the leadership of Bao Dai, as a government created by the French and considered an ally of the French Union. Its primary mission was to support the French military against the resistance movement led by the Democratic Republic of Vietnam, led by President Ho Chi Minh.

Following the Battle of Dien Bien Phu in 1954 and the signing of the Geneva Accords, the State of Vietnam, along with the French, concentrated its efforts in the southern region along the 17th parallel of Vietnam. According to the plan, the French would gradually withdraw within two years, and Vietnam would proceed with nationwide general elections for reunification. However, concerns from the CIA regarding the potential victory of Ho Chi Minh and the establishment of a unified government led to U.S. intervention. The State of Vietnam received backing to prevent the elections and permanently divide Vietnam into two nations. The U.S. aimed to establish an anti-Communist government in South Vietnam, regardless of its commitment to democracy.

With support from the United States, the State of Vietnam was equipped militarily and financially to replace the French. This assistance not only helped sustain the administrative apparatus and the military but also facilitated the transition from French to American strategies and weaponry.

Prime Minister Ngo Dinh Diem assumed the presidency, and subsequently, the country organized parliamentary elections, leading to the promulgation of the constitution and the establishment of the Republic of Vietnam. However, Diem's regime faced internal conflicts, particularly in religious matters, and notable events such as the 1963 Vesak crisis stirred opposition and eroded Western support.

In 1963, the government of the First Republic was overthrown by a group of military leaders in the south of Vietnam, those were Diem’s subordinates, and the United States officially entered the war by deploying combat troops to Da Nang, a city in the middle of Vietnam. Subsequent events led to the formation of the Second Republic of Vietnam, with efforts to ensure political stability, including the 1967 elections and the promulgation of the constitution in April 1967, serving as the legal foundation for the country until April 30, 1975.