The Japanese coup d'état in French Indochina, known as Meigo Sakusen (Operation Bright Moon), was a Japanese operation that took place on 9 March 1945 towards the end of World War II. With Japanese forces losing the war and the threat of an Allied invasion of Indochina imminent, the Japanese were concerned about an uprising against them by French colonial forces.
Despite the French having anticipated an attack, the Japanese struck in a military campaign attacking garrisons all over the colony. The French were caught off guard and all of the garrisons were overrun with some then having to escape to Nationalist China where they were harshly interned. The Japanese replaced French officials, and effectively dismantled their control of Indochina. The Japanese were then able to install and create a new Empire of Vietnam, Kingdom of Cambodia and Kingdom of Laos which under their direction would acquiesce with their military presence and forestall a potential invasion by the Allies.
French Indochina comprised the colony of Cochinchina and the protectorates of Annam, Cambodia and Tonkin, and the mixed region of Laos. After the fall of France in June 1940 the French Indochinese government had remained loyal to the Vichy regime. The following month governor Admiral Jean Decoux signed an agreement under which Japanese forces were permitted to occupy bases across Indochina. In September the same year Japanese troops invaded and took control of Northern Indochina, and then in July 1941 they occupied the Southern half as well. The Japanese allowed Vichy French troops and the administration to continue on albeit as puppets.
By 1944 with the war going against the Japanese after defeats in Burma and the Philippines they then feared an Allied offensive in French Indochina. The Japanese were already suspicious of the French; the liberation of Paris in August 1944 raised further doubts as to where the loyalties of the colonial administration lay. 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 Decoux got a cold response from de Gaulle and was stripped of his powers as governor general but was ordered to maintain his post with orders to deceive the Japanese. Instead Decoux's army commander General Eugène Mordant (fr), 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 incapacity 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.
British intelligence, mission Force 136 air-dropped several Free French operatives into Indochina in late 1944. They provided detailed information on targets mostly related to ship movements along the coast to British headquarters in India and China, who then in turn transmitted them to the Americans, During the South China Sea raid in January 1945 American carrier 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. The French refused to give the Americans up and when the Japanese prepared to storm the prison the men were smuggled out. The Japanese demanded their surrender but Decoux refused and General Yuitsu Tsuchihashi, the Japanese commander, decided to act. Tsuchihashi could no longer trust Decoux to control his subordinates and asked for orders from Tokyo. The Japanese High Command were reluctant for another front to be opened up in an already poor situation. Nevertheless, they ordered Tsuchihashi to offer Decoux an ultimatum and if this was rejected then at his discretion a coup would be authorised  With this coup the Japanese planned to overthrow the colonial administration and intern or destroy the French army in Indochina. Several friendly puppet governments would then be established and win the support of the indigenous populations.
In early 1945 the French Indochina army still outnumbered the Japanese and comprised about 65,000 men, of whom 48,500 were locally recruited Tirailleurs indochinois under French officers. The remainder were French regulars of the Colonial Army plus three battalions of the Foreign Legion. A separate force of indigenous gardes indochinois (gendarmerie) numbered 27,000. Since the fall of France in June 1940 no replacements or supplies had been received from outside Indochina. By March 1945 only about 30,000 French troops could be described as fully combat ready, the remainder serving in garrison or support units. 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.
In early March 1945 Japanese forces were redeployed around the main French garrison towns throughout Indochina, linked by radio to the Southern area headquarters. French officers and civilian officials were however forewarned of an attack through troop movements, and some garrisons were put on alert. The Japanese envoy in Saigon Ambassador Shunichi Matsumoto declared to Decoux that since an Allied landing in Indochina was inevitable, Tokyo command wished to put into place a "common defence" of Indochina. Decoux however resisted stating that this would be a catalyst for an Allied invasion but suggested that Japanese control would be accepted if they actually invaded. This was not enough and the Tsuchihashi accused Decoux of playing for time.
On 9 March, after more stalling by Decoux, Tsuchihashi delivered an ultimatum for French troops to disarm. Decoux sent a messenger to Matsumoto urging further negotiations but the message arrived at the wrong building. Tsuchihashi, assuming that Decoux had rejected the ultimatum, immediately ordered commencement of the coup.
That evening Japanese forces moved against the French in every center. 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. 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. Instead, Thailand began negotiating with the Japanese over their course of action, and by the end of March they hadn't fully complied with the demands. Dōmei Radio (the official Japanese propaganda channel) announced that pro-Japanese independence organizations in Tonkin formed a federation to promote a free Indochina and cooperation with the Japanese.
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. Three hundred men, one third of them French, managed to elude the Japanese and escape to the A Sầu Valley. However, over the next three days, they succumbed to hunger, disease and betrayals - many surrendered while others fought their way into Laos where only a handful survived. Meanwhile, Mordaunt led opposition by the garrison of Hanoi for several hours but was forced to capitulate.
An attempt to disarm a group of Vietnamese partisans ended badly for the Japanese when 600 of them marched into Quảng Ngãi. The Vietnamese nationalists had been armed with automatic weapons supplied by the OSS parachuted nearby by at Kontum. The Japanese had been led to believe that these men would readily defect but the Vietnamese ambushed the Japanese. Losing only three killed and seventeen wounded they inflicted 143 killed and another 205 wounded on the Japanese before they too were overcome. A much bigger force of Japanese came the next day but they found the garrison empty. In Annam and Cochinchina only token resistance was offered and most garrisons, small as they were, surrendered.
Further north the French had the sympathy of many indigenous peoples. Several hundred Laotians volunteered to be armed as guerrillas against the Japanese; French officers organized them into detachments but turned away those they did not have weapons for.
In Haiphong the Japanese assaulted the Bouet barracks: headquarters of Colonel Henry Lapierre's 1st Tonkin Brigade. Using heavy mortar and machine gun fire, one position was taken after another before the barracks fell and Lapierre ordered a ceasefire. Lapierre refused to sign surrender messages for the remaining garrisons in the area. Codebooks had also been burnt which meant the Japanese then had to deal with the other garrisons by force.
In Laos, Vientiane, Thakhek and Luang Prabang were taken by the Japanese without much resistance. In Cambodia the Japanese with 8,000 men seized Phnom Penh and all major towns in the same manner. All French personnel in the cities on both regions were either interned or in some cases executed.
The Japanese strikes at the French in the Northern Frontier in general saw the heaviest fighting. One of the first places they needed to take and where they amassed the 22nd division was at Lang Son, a strategic fort near the Chinese border.
The defences of Lang Son consisted of a series of fort complexes built by the French to defend against a Chinese invasion. The main fortress was the Fort Brière de l'Isle - inside was a French garrison of nearly 4,000 men, many of them Tonkinese, with units of the French Foreign Legion. Once the Japanese had cut off all communication's to the forts they invited General Émile Lemonnier, the commander of the border region, to a banquet of the headquarters of the 22nd division of the Imperial Japanese Army. Lemonnier declined to attend the event, but allowed some of his staff to go in his place. They were taken prisoner and soon after the Japanese bombarded Fort Brière de l'Isle attacking with infantry and tanks. The small forts outside had to defend themselves in isolation; they did so for a time, proving impenetrable, and the Japanese were repelled with some loss. They tried again the next day and succeeded in taking the outer positions. Finally the main fortress of Brière de l'Isle was overrun and taken after heavy fighting.
Lemonnier was subsequently taken prisoner himself and ordered by a Japanese general to sign a document formally surrendering the forces under his command. Lemonnier refused to sign the documents. As a result the Japanese took him outside where they forced him to dig a grave along with French Resident-superior (Résident-général) Camille Auphelle. Lemonnier again was ordered to sign the surrender documents and again refused - the Japanese subsequently beheaded him. The Japanese then machine-gunned some of the prisoners and either beheaded or bayoneted the wounded survivors.
The battle of Lang Son cost the French heavy casualties and their force on the border was effectively destroyed. European losses were 544 killed, of which 387 had been executed after capture. In addition 1,832 Tonkinese colonial troops were killed (including 103 who were executed) while another 1,000 were taken prisoner. On March 12 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. Reportedly between 400 and 600 of the prisoners were killed or wounded.
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. Following Lemonnier's refusal to order a general surrender, the Japanese launched an attack against the town. The French resisted for three days. The Japanese were then reinforced by two regiments from 22nd Division from Lang Son and finally overran the French colonial force. Fifty three survivors were beheaded or bayoneted to death.
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. However they were soon harried by the Japanese air force and artillery fire, being forced to abandon all their heavy equipment as they crossed the Red River. Sabattier then found that the Japanese had blocked the most important border crossings at Lao Cai and Ha Giang during the reductions Lang Son and Dang Dong. Contact was then lost with Major-General Marcel Alessandri' s 2nd Tonkin Brigade, numbering some 5,700 French and colonial troops. This column included three Foreign Legion battalions of the 5eme Etranger. Their only option was to fight their own way to China.
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. Both countries ordered that their forces provide no assistance to the French, but American general Claire Lee Chennault went against orders, and aircraft from his 51st Fighter Group and 27th Troop Carrier Squadron flew support missions as well as dropping medical supplies for Sabbattier's forces retreating into China. 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.
By mid April Alessandri, having realised he was on his own, split his force into two. Soon a combination of disease, ration shortages and low morale forced him into a difficult decision. 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. Many of the tirailleurs were far from their homes and some were captured by the Japanese. Others joined the Viet Minh. 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. 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.
By this time de Gaulle had been informed of the situation in Indochina and then swiftly told Sabbattier via radio orders to maintain a presence in Indochina for the sake of France's pride at all costs. By May 6 however many of the remaining members of the Tonkin Division were over the Chinese border where they were interned under harsh conditions. Between March 9 and May 2 the Tonkin division had suffered heavily; many had died or were invalided by disease. In combat 774 had been killed and 283 wounded with another 303 missing or captured.
During the Coup the Japanese urged the declarations of independence from the traditional rulers of the different regions, creating a new Empire of Vietnam, Kingdom of Cambodia and Kingdom of Laos under their direction. Emperor Bảo Đại complied in Vietnam where they set up a puppet government headed by Tran Trong Kim and which collaborated with the Japanese. King Norodom Sihanouk also obeyed, but the Japanese did not trust the francophile monarch.
Nationalist leader Son Ngoc Thanh, who had been exiled in Japan and was considered a more trustworthy ally than Sihanouk, returned to Cambodia and became Minister of foreign affairs in May and then Prime Minister in August. In Laos however, King Sisavang Vong, who favoured French rule, refused to declare independence, finding himself at odds with his Prime Minister, Prince Phetsarath Rattanavongsa.
On 15 May with the Coup ended and independence granted, General Tsuchihashi declared mopping up operations complete and released several brigades to other fronts.
The coup had, in the words of diplomat Jean Sainteny, "wrecked a colonial enterprise that had been in existence for 80 years."
French losses were heavy – in total 15,000 French soldiers were held prisoner by the Japanese. Nearly 4,200 were killed with many executed after surrendering - about half of these were European or French metropolitan troops. Practically all French civil and military leaders as well plantation owners were made prisoners, including Decoux. They were confined either in specific districts of big cities or in camps. Those who were suspected of armed resistance were jailed in the Kempeitai prison in bamboo cages and were tortured and cruelly interrogated. The locally recruited tirailleurs and gardes indochinois who had made up the majority of the French military and police forces, effectively ceased to exist. About a thousand were killed in the fighting or executed after surrender. Some joined pro-Japanese militias or Vietnamese nationalist guerrillas. Deprived of their French cadres, many dispersed to their villages of origin. Over three thousand reached Chinese territory as part of the retreating French columns.
What was left of the French forces that had escaped the Japanese attempted to join the resistance groups where they had more latitude for action in Laos. The Japanese there had less control over this part of the territory and with Lao guerilla groups managed to gain control of several rural areas. Elsewhere the resistance failed to materialize as the Vietnamese refused to help the French. They also lacked precise orders and communications from the provisional government as well as the practical means to mount any large-scale operations.
In northern Vietnam, Ho Chi Minh's Viet Minh started their own guerilla campaign with the help of the American OSS who trained, supplied them with arms and funds. The famine in Vietnam had caused resentment among the population both towards the French and the Japanese (although US bombing played a part). They established their bases in the countryside without meeting much resistance from the Japanese who were mostly present in the cities. Viet Minh numbers increased especially when they ransacked 75 - 100 warehouses, dispersed the rice and refused to pay taxes. In July OSS with the Viet Minh - some of whom were remnants of Sabattiers division - went over the border to conduct operations. Their actions were limited to a few attacks against Japanese military posts. Most of these were unsuccessful however as the Viet Minh lacked the military force to launch any kind of attack against the Japanese.
Japan surrendered when Emperor Hirohito announced Japan's capitulation on 16 August. Soon after Japanese garrisons officially handed control to Bảo Đại in the North and the United Party in the South. This, however, allowed nationalist groups to take over public buildings in most of the major cities. The Viet Minh were thus presented with a power vacuum, and on the 19th the August Revolution commenced. 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. The Japanese did not oppose the Viet Minh's takeover as they were reluctant to let the French retake control of their colony. Ho Chi Minh proclaimed Vietnam's independence on 2 September 1945.
Charles de Gaulle in Paris criticized the United States, United Kingdom and China for not helping the French in Indochina during the coup. De Gaulle however affirmed that France would regain control of Indochina.
French Indochina had been left in chaos by the Japanese occupation. On 11 September British and Indian troops of the 20th Indian Division under Major General Douglas Gracey arrived at Saigon as part of Operation Masterdom. At the same time China's National Revolutionary Army entered the North of the country. After the Japanese surrender all French prisoners had been gathered on the outskirts of Saigon and Hanoi and the sentries disappeared altogether on September 18. The six months spent in captivity cost an additional 1,500 lives. By September 22, 1945, all prisoners were liberated by Gracey's men and were then armed and dispatched in combat units towards Saigon to conquer it from the Vietminh. They were later joined by the French Far East Expeditionary Corps (which had been established to fight the Japanese), having arrived a few weeks later.
On March 25, 1957, the former Rue des Tuileries (1st district of Paris) was renamed Avenue Général-Lemonnier in honour of the French general who refused to capitulate at the Battle of Lang Son. A plaque is located there describing the general's heroic refusal to surrender.