After the 1954 Geneva Agreements, the State of Vietnam abandoned its sovereignty over the northern part of the country, which was controlled by the Việt Minh.

Ngô Đình Diệm was appointed prime minister the same year and—after having ousted Bảo Đại in 1955—became president of the Republic of Vietnam.

The Democratic Republic of Vietnam was established by the Việt Minh on September 2, 1945 (the same day Japan signed surrender documents with the United States).

By February 1947, following the pacification of Tonkin (Northern Vietnam), the Tonkinese capital, Hanoi, and the main traffic axis returned to French control.

In order to reduce Việt Minh leader Hồ Chí Minh’s influence over the Vietnamese population, the French authorities in Indochina supported the return to power of Bảo Đại (the last emperor of the Nguyễn Dynasty), by establishing puppet states, including the State of Vietnam.

On June 5, 1948, the Halong Bay Agreements (Accords de la baie d’Along) allowed the creation of a unified Vietnamese government replacing the governments of Tonkin (North Vietnam) and Annam (Middle Vietnam) associated to France within the French Union and the Indochinese Federation then including the neighboring Kingdom of Laos and Kingdom of Cambodia.

The massive semi-voluntary migration of anti-communist north Vietnamese, essentially Roman Catholic people, proceeded during the French-American Operation Passage to Freedom from 1954 to 1955.

[7] During the election, Diệm's brother Ngô Đình Nhu and the Personalist Labor Revolutionary Party (commonly known as "Cần Lao Party") supplied Diệm's electoral base in organizing and supervising the elections, especially the propaganda campaign for destroying Bảo Đại's reputation.

[10] The Domain of the Crown (Vietnamese: Hoàng triều Cương thổ / 皇朝疆土; French: Domaine de la Couronne) was originally the Nguyễn dynasty's geopolitical concept for its protectorates and principalities where the Kinh ethnic group didn't make up the majority, later it became a type of administrative unit of the State of Vietnam.

[11] In the areas of the Domain of the Crown Chief of State Bảo Đại was still officially (and legally) titled as the "Emperor of the Nguyễn dynasty".