During World War II, in 1940, Japan invaded Indochina. At the 8th Congress of the Đảng Cộng sản Đông Dương (English: Indochinese Communist Party) (1930-1945), itself a merger of the An Nam cộng sản Đảng (English: Communist Party of Annam, 1929-1930) and the Đông Dương Cộng sản Liên đoần (English: Indochinese Communist League) (1929-1930) (previously the Tân Việt Cách mệnh Đảng (English: Revolutionary Party of the New Viet Nam) (1925-1930) under the leadership of Hồ Chí Minh, took the decision to establish the Việt Nam Độc Lập Đồng Minh Hội (English: League for the Independence of Viet Nam; French: Ligue pour l'indépendance du Viêt Nam, colloquially known as National Liberation Front, NLF), on 19 May 1941 for the purpose of self-government of the Vietnamese People in Indochina, an appeal even made formally to members of the Versailles Peace talks (formally: Paris Peace Conference (1919)) by a group of Vietnamese, also led by him.
When the Japanese surrendered on 15 August 1945, the Việt Minh immediately launched the insurrection, Cách mạng tháng Tám (English: August Revolution) together with the Vanguard Youth against France which they had already prepared for a long time. 'People's Revolutionary Committees' across the countryside took over administrative positions, often acting on their own initiative, while in the cities the Japanese stood by as the Vietnamese took control. On the morning of 19 August, the Việt Minh took control of Hanoi, seizing the vast majority of northern Viet Nam in the next few days. Tran Trong Kim's government had resigned earlier, on 13 August, yielding to Hồ Chí Minh's new "Vietnamese Provisional Government" (unofficial label). Hồ Chí Minh offered Emperor Bảo Đại a position as supreme advisor. 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 the emperor (last ruler of the Nguyễn Dynasty), Bảo Đại, by establishing him as Head of State a "State of Viet Nam" (unofficial name), which in reality was a puppet state. Bảo Đại had voluntarily abdicated on 25 August 1945 (at the request of Hồ Chí Minh), after the fall of the short-lived Empire of Viet Nam established by France. However, Hồ Chí Minh issued the Proclamation of Independence of the Democratic Republic of Vietnam (English: Proclamation of Independence of the Democratic Republic of Viet Nam) for the newly established Việt Nam Dân Chủ Cộng Hòa (English: Democratic Republic of Viet Nam), headquartered in Hanoi, on 2 September 1945 after controlling most of the country. However, his government was not recognized by any country. Besides that, he had also hosted the 1946 Vietnamese National Assembly election with the participation of 89% of the voters in Viet Nam (North and South). The Democratic Republic of Viet Nam had officially become the constitutional representatives of Viet Nam in 1946.
By February 1947, following the pacification of Tonkin (North Vietnam), the Tonkinese capital, Hanoi, and the main traffic axis returned to French control. The Việt Minh partisans were forced to retreat into the jungle and prepared to pursue the war using guerrilla warfare.
On 5 June 1948, the Halong Bay Agreements (Accords de la baie d’Along) allowed the creation of a unified Vietnamese government replacing the Tonkin (North Viet Nam), Annam (Middle Viet Nam) associated to France within the French Union and the Indochinese Federation then including the neighboring Kingdom of Laos and Kingdom of Cambodia. Cochinchina (South Viet Nam), however, had a different status, both as a colony and as an autonomous republic, and its reunification with the rest of Viet Nam had to be approved by its local assembly, and then by the French National Assembly. During the transitional period, a Provisional Central Government of Viet Nam was proclaimed: Nguyễn Văn Xuân, until then head of the Provisional Government of South Viet Nam (as Cochinchina had been known since 1947) became its president, while Bảo Đại waited for a complete reunification to take office.
On 8 March 1949, after the élysée Accords, the State of Vietnam was recognized by France as an independent country ruled by Vietnamese Emperor Bảo Đại, as an "associated state" within the French Union under Bảo Đại. However, France still controlled all foreign relations and every defense issue. The Việt Minh quickly denounced the government and stated that they wanted "real independence, not Bảo Đại independence." Later, as a concession to the new government and a way to increase their popularity numbers, France agreed to the formation of the Vietnamese National Army commanded by Vietnamese officers. These troops were used mostly to garrison quiet sectors, so French forces would be available for combat. Private armies from the Cao Đài and Hòa Hảo religious sects and the Bình Xuyên crime syndicate were used in the same way.
December 19, 1946 marked the beginning of the (First) Indochina War: after the bombing of the port of Haiphong on 23 November 1946 by the artillery of the French Army, the Việt Minh decided to launch an offensive aimed at liberating the city of Hanoi. At 8 pm, an explosion in the city's power station heralded the beginning of the insurgency. French nationals were massacred and houses looted. Hồ Chí Minh called on the Vietnamese people to rise against the French presence which turned into a war that formally ended by 1954 Geneva Conference Provisions, published on 21 July 1954 (other sources cite the formal end on 1 August 1954).
Background: Length = a, width = 2/3 of a.
Star: From the centre of the vertex of one acute angle = 1/5 a; from the centre to one obtuse angle = 1/10 a.
Placement of star: The yellow star has 5 acute angles and 5 obtuse angles, its centre falls in the centre of the flag, one acute angle points directly upwards along the vertical median of the flag.
The star in the 1945 flag is made in such a way that the inscribed circle (i.e., the one touching the inner angles) is half the diameter of the circumscribed circle (that touches the outer points). Adopted 29 September, 1945.