After the fall of France in June 1940 the French Indochinese government had remained loyal to the Vichy regime, which collaborated with the Axis powers.

The following month governor Admiral Jean Decoux signed an agreement under which Japanese forces were permitted to occupy bases across Indochina.

[10] The Vichy regime by this time had ceased to exist, but its colonial administration was still in place in Indochina, though Decoux had recognized and contacted the Provisional Government of the French Republic led by Charles de Gaulle.

[12] Instead Decoux's army commander General Eugène Mordant secretly became the Provisional Government's delegate and the head of all resistance and underground activities in Indochina.

Mordant however was careless – he was too talkative and had an inability to keep his preparations secret, so much so that the Japanese Kempeitai swiftly uncovered the plot against them and discussed the next move against the French.

They provided detailed information on targets, mostly related to ship movements, along the coast to British headquarters in India and China, who in turn transmitted them to the Americans.

[13] During the South China Sea raid in January 1945 American carriers' aircraft sank twenty-four vessels and damaged another thirteen.

Six U.S. navy pilots were shot down but were picked up by French military authorities and housed in the central prison of Saigon for safe keeping.

[18] At the beginning of 1945, the understrength Japanese Thirty-Eighth Army was composed of 30,000 troops, a force that was substantially increased by 25,000 reinforcements brought in from China, Thailand, and Burma in the following months.

[19] Despite an initial disparity in numbers, the disciplined, well-equipped and battle-hardened Japanese troops enjoyed local superiority over their French counterparts even prior to the coup.

[20] In early March 1945 Japanese forces were redeployed around the main French garrison towns throughout Indochina, linked by radio to the Southern area headquarters.

[2] In some instances French troops and the Garde Indochinoise were able to resist attempts to disarm them, with the result that fighting took place in Saigon, Hanoi, Haiphong and Nha Trang and the Northern frontier.

[2] Japan issued instructions to the government of Thailand to seal off its border with Indochina and to arrest all French and Indochinese residents within its territory.

[23] The 11th R.I.C (régiment d'infanterie coloniale) based at the Martin de Pallieres barracks in Saigon were surrounded and disarmed after their commanding officer, Lieutenant-Colonel Moreau, was arrested.

In Hue there was sporadic fighting; the Garde Indochinoise, who provided security for the résident supérieur, fought for 19 hours against the Japanese before their barracks was overrun and destroyed.

Meanwhile, Mordant led opposition by the garrison of Hanoi for several hours but was forced to capitulate, with 292 dead on the French side and 212 Japanese.

[2] On 12 March planes of the US Fourteenth Air Force flying in support of the French, mistook a column of Tonkinese prisoners for Japanese and bombed and strafed them.

[2] On the 12th the Japanese then advanced further north to the border town of Dong Dang where a company of the 3rd Regiment of Tonkinese Rifles and a battery of colonial artillery were based.

[25] In the North West General Gabriel Sabattier's Tonkin division had enough time to be spared an assault by the Japanese and were able to retreat northwest from their base in Hanoi, hoping to reach the Chinese border.

[2] Sabattier then found that the Japanese had blocked the most important border crossings at Lao Cai and Ha Giang during the reductions of Lang Son and Dang Dong.

[30] The United States and China were reluctant to start a large-scale operation to restore French authority, as they did not favour colonial rule, and had little sympathy for the Vichy regime which had formerly collaborated with the Japanese.

[1] Between 12 and 28 March, the Americans flew thirty-four bombing, strafing and reconnaissance missions over the North of Indochina but they had little effect in stemming the Japanese advance.

With reluctance he disarmed and disbanded his locally recruited colonial troops, leaving them to their fate in a measure which angered French and Vietnamese alike.

The remaining French and Foreign Legion units gradually discarded all of their heavy weapons, motor vehicles and left behind several tons of ammunition without destroying any of it.

[25] The division were soon reduced in numbers by disease and missing men as they moved towards Son La and Dien Bien Phu where they fought costly rearguard actions.

On 11 March 1945, Emperor Bảo Đại was permitted to announce the Vietnamese "independence"; this declaration had been prepared by Yokoyama Seiko, Minister for Economic Affairs of the Japanese diplomatic mission in Indochina and later advisor to Bao Dai[32] Bảo Đại complied in Vietnam where they set up a puppet government headed by Tran Trong Kim[33] and which collaborated with the Japanese.

[34] In Laos however, King Sisavang Vong of Luang Phrabang, who favoured French rule, refused to declare independence, finding himself at odds with his Prime Minister, Prince Phetsarath Ratanavongsa, but eventually acceded on 8 April.

[36] The locally recruited tirailleurs and gardes indochinois who had made up the majority of the French military and police forces, effectively ceased to exist.

[8] On 25 August, Bảo Đại was forced to abdicate in favour of Ho and the Viet Minh - they took control of Hanoi and most of French Indochina.

After the Japanese surrender all French prisoners had been gathered on the outskirts of Saigon and Hanoi and the sentries disappeared altogether on 18 September.