Vietnam was absorbed into French Indochina in stages between 1858 and 1887. Nationalism grew until World War II provided a break in French control. Early Vietnamese resistance centered on the intellectual Phan Bội Châu. Châu looked to Japan, which had modernized and was one of the few Asian nations to successfully resist European colonization.
Due to French pressure, Japan deported Phan Bội Châu to China. Witnessing Sun Yat-sen's Xinhai Revolution, Châu was inspired to commence the Viet Nam Quang Phục Hội movement in Guangzhou. From 1914 to 1917, he was imprisoned by Yuan Shikai's counterrevolutionary government.
In 1925, Phan Bội Châu was captured by French agents in Shanghai and spirited to Vietnam.
Japan launched its invasion of French Indochina, mirroring its ally Germany's conquest of metropolitan France.
From October 1940 to May 1941, during the Franco-Thai War, the Vichy French in Indochina defended their colony in a border conflict in which the forces of Thailand invaded while the Japanese sat on the sidelines.
Due to his popularity, Châu was spared from execution and placed under house arrest until his death in 1940.
Thai military successes were limited to the Cambodian border area, and in January 1941 Vichy France's modern naval forces soundly defeated the inferior Thai naval forces in the Battle of Ko Chang. The war ended in May, with the French agreeing to minor territorial revisions which restored formerly Thai areas to Thailand.
An armistice was signed between Japan and the United States on August 20, 1945. The Provisional Government of the French Republic wanted to restore its colonial rule in French Indochina as the final step of the Liberation of France.
During the Vietnamese Famine of 1945, Hồ Chí Minh blamed ruthless Japanese exploitation and poor weather for up to two million Vietnamese deaths. The Việt Minh arranged a relief effort in the north, winning wide support there as a result.
In March 1945, Japan launched the Second French Indochina Campaign to oust the Vichy French and formally installed Emperor Bảo Đại as head of the nominally independent Empire of Vietnam. The Japanese arrested and imprisoned most of the French officials and military officers remaining in the country.
At the Potsdam Conference in July 1945, the Combined Chiefs of Staff decided that Indochina south of latitude 16° north was to be included in the Southeast Asia Command under British Admiral Mountbatten. Japanese forces located south of that line surrendered to him and those to the north surrendered to Generalissimo Chiang Kai-shek.
Japanese forces allowed the Việt Minh and other nationalist groups to take over public buildings and weapons without resistance, which began the August Revolution. On August 25, Hồ Chí Minh was able to persuade Emperor Bảo Đại to abdicate. Bảo Đại was appointed "supreme advisor" to the new Việt Minh-led government in Hanoi.
In September 1945, Chinese forces entered Tonkin, and a small British task force landed at Saigon.
On V-J (Victory on Japan) Day, September 2, Hồ Chí Minh had proclaimed in Hanoi the establishment of the Democratic Republic of Vietnam (DRV).
On September 13, 1945, a Franco-British task force landed in Java, main island of the Dutch East Indies (for which independence was being sought by Sukarno), and Saigon, capital of Cochinchina (southern part of French Indochina), both being occupied by the Japanese and ruled by Field Marshal Hisaichi Terauchi, Commander-in-Chief of Japan's Southern Expeditionary Army Group based in Saigon.
Allied troops in Saigon were an airborne detachment, two British companies of the Indian 20th Infantry Division and the French 5th Colonial Infantry Regiment, with British General Sir Douglas Gracey as supreme commander. The latter proclaimed martial law on September 21. The following night the Franco-British troops took control of Saigon.
On 23 September 1945, with the knowledge of the British commander in Saigon, French forces overthrew the local DRV (the Democratic Republic of Vietnam) government, and declared French authority restored in Cochinchina.
On October 9, 1945, General Leclerc arrived in Saigon, accompanied by French Colonel Massu's March Group (Groupement de marche). Leclerc's primary objectives were to restore public order in south Vietnam and to militarize Tonkin (north Vietnam). Secondary objectives were to wait for French backup in view to take back Chinese-occupied Hanoi, then to negotiate with the Việt Minh officials.
In early 1946, the French landed a military force at Haiphong, and negotiations took place about the future for Vietnam as a state within the French Union. Fighting broke out in Haiphong between the Việt Minh government and the French over a conflict of interest in import duty at the port.
Chiang Kai-shek threatened the French with war in response to manoeuvering by the French and Hồ Chí Minh against each other, forcing them to come to a peace agreement. In February 1946, he also forced the French to surrender and renounce all of their concessions and ports in China, such as Shanghai, in exchange for withdrawing from northern Indochina and allowing French troops to reoccupy the region starting in March 1946.
On November 23, 1946, the French fleet began a naval bombardment of the Vietnamese sections of Haiphong that killed over 6,000 Vietnamese civilians in one afternoon. The Việt Minh quickly agreed to a cease-fire and left the cities. This is known as the Haiphong incident.
After over one year of latent conflict, all-out war broke out in December 1946 between French and Việt Minh forces as Hồ Chí Minh and his government went underground.
The first occurrence was probably at the National Assembly on March 21, 1947, when the communist deputes refused to back the military credits for Indochina.
In 1948, France started looking for means of opposing the Việt Minh politically, with an alternative government in Saigon. They began negotiations with the former emperor Bảo Đại to lead an "autonomous" government within the French Union of nations, the State of Vietnam.
In 1949, France officially recognized the nominal "independence" of the State of Vietnam 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". Within the framework of the French Union, France also granted independence to the other nations in Indochina, the Kingdoms of Laos and Cambodia.
The French tried to stabilize Indochina by reorganizing it as a Federation of Associated States. In 1949, they put former Emperor Bảo Đại back in power, as the ruler of a newly established State of Vietnam.
By January 1950, Hồ Chí Minh's government gained recognition from China and the Soviet Union. In the same year, the government of Bảo Đại gained recognition by the United States and the United Kingdom.
On June 30, 1950, the first U.S. supplies for Indochina were delivered. In September, Truman sent the Military Assistance Advisory Group (MAAG) to Indochina to assist the French.
Major general Thái attacked Đông Khê on September 15, and Đông Khê fell on September 18.
On January 13, 1951, Giáp moved the 308th and 312th Divisions, made up of over 20,000 men, to attack Vĩnh Yên, 20 miles (32 km) northwest of Hanoi, which was manned by the 6,000-strong 9th Foreign Legion Brigade.
By January 16, the Battle of Vĩnh Yên ended as Giáp was forced to withdraw, with over 6,000 of his troops killed, 8,000 wounded and 500 captured.
USS Windham Bay delivered Grumman F8F Bearcat fighter aircraft to Saigon on January 26, 1951.
On March 23, Giáp tried again, launching an attack against Mạo Khê, 20 miles (32 km) north of Haiphong. The 316th Division, composed of 11,000 men, with the partly rebuilt 308th and 312th Divisions in reserve, went forward and were beaten in bitter hand-to-hand fighting against French troops. Giap withdrew, having lost around 500 troops (by Việt Minh estimation) to over 3,000 (by French estimation) dead and wounded by March 28.
Giáp launched yet another attack, the Battle of the Day River, on May 29 with the 304th Division at Phủ Lý, the 308th Division at Ninh Bình, and the main attack delivered by the 320th Division at Phat Diem south of Hanoi.
On July 31, French General Charles Chanson was assassinated during a propaganda suicide attack at Sa Đéc in South Vietnam that was blamed on the Việt Minh although it was argued in some quarters that Cao Đài nationalist Trình Minh Thế could have been involved in its planning.
On November 14, 1951, the French seized Hòa Bình, 25 miles (40 km) west of the De Lattre Line, by a parachute drop and extended their perimeter.
In January, General de Lattre fell ill from cancer and had to return to France for treatment. He died there shortly thereafter and was replaced by General Raoul Salan as the overall commander of French forces in Indochina.
The Việt Minh launched attacks on Hòa Bình, forcing the French to withdraw back to their main positions on the De Lattre line by February 22, 1952.
In the Battle of Nà Sản, starting on October 2, French commanders began using "hedgehog" tactics, consisting in setting up well-defended outposts to get the Việt Minh out of the jungle and force them to fight conventional battles instead of using guerrilla tactics.
On October 17, 1952, Giáp launched attacks against the French garrisons along Nghĩa Lộ, northwest of Hanoi, and overran much of the Black River valley, except for the airfield of Nà Sản where a strong French garrison entrenched.
On October 29, 1952, in the largest operation in Indochina to date, 30,000 French Union soldiers moved out from the De Lattre line to attack the Việt Minh supply dumps at Phú Yên.
Salan took Phú Thọ on November 5.
Salan took Phu Doan on November 9 by a parachute drop.
Salan took Phú Yên on November 13.
Salan correctly guessed what the Việt Minh were up to and cancelled the operation on November 14, beginning to withdraw back to the De Lattre Line.
The only major fighting during the operation came during the withdrawal, when the Việt Minh ambushed the French column at Chan Muong on November 17.
On April 9, 1953, Giáp, after having failed repeatedly in direct attacks on French positions in Vietnam, changed strategy and began to pressure the French by invading Laos, surrounding and defeating several French outposts such as Muong Khoua.
In May, General Henri Navarre replaced Salan as supreme commander of French forces in Indochina. He reported to the French government "... that there was no possibility of winning the war in Indo-China", saying that the best the French could hope for was a stalemate.
Operation Castor was launched on November 20, 1953, with 1,800 men of the French 1st and 2nd Airborne Battalions dropping into the valley of Điện Biên Phủ and sweeping aside the local Việt Minh garrison. The paratroopers gained control of a heart-shaped valley 12 miles (19 km) long and 8 miles (13 km) wide surrounded by heavily wooded hills. Encountering little opposition, the French and Tai units operating from Lai Châu to the north patrolled the hills.
By 1954, despite official propaganda presenting the war as a "crusade against communism", the war in Indochina was still growing unpopular with the French public. The political stagnation of the Fourth Republic meant that France was unable to extract itself from the conflict.
The Battle of Dien Bien Phu occurred in 1954 between Việt Minh forces under Võ Nguyên Giáp, supported by China and the Soviet Union, and the French Union's French Far East Expeditionary Corps, supported by US financing and Indochinese allies. The battle was fought near the village of Điện Biên Phủ in northern Vietnam and became the last major battle between the French and the Vietnamese in the First Indochina War.
With French supply lines interrupted, the French position became untenable, particularly when the advent of the monsoon season made dropping supplies and reinforcements by parachute difficult. With defeat imminent, the French sought to hold on until the opening of the Geneva peace meeting on April 26. The last French offensive took place on May 4, but it was ineffective. The Việt Minh then began to hammer the outpost with newly supplied Soviet Katyusha rockets and other weaponry provided by communist allies.
The final fall took two days, May 6 and 7, during which the French fought on but were eventually overrun by a huge frontal assault. General Cogny, based in Hanoi, ordered General de Castries, who was commanding the outpost, to cease fire at 5:30 pm and to destroy all materiél (weapons, transmissions, etc.) to deny their use to the enemy. A formal order was given to not use the white flag so that the action would be considered a ceasefire instead of a surrender. Much of the fighting ended on May 7; however, the ceasefire was not respected on Isabelle, the isolated southern position, where the battle lasted until May 8, 1:00 am.
Negotiations between France and the Việt Minh started in Geneva in April 1954 at the Geneva Conference, during which time the French Union and the Việt Minh were fighting a battle at Điện Biên Phủ. In France, Pierre Mendès France, opponent of the war since 1950, had been invested as Prime Minister on June 17, 1954, on a promise to put an end to the war, reaching a ceasefire in four months.
One month after Điện Biên Phủ, the composite Groupe Mobile 100 (GM100) of the French Union forces evacuated the An Khê outpost and was ambushed by a larger Việt Minh force at the Battle of Mang Yang Pass from June 24 to July 17.
At the International Geneva Conference on July 21, 1954, the new socialist French government and the Việt Minh made an agreement which effectively gave the Việt Minh control of North Vietnam above the 17th parallel. The south continued under Bảo Đại. The agreement was denounced by the State of Vietnam and by the United States. A year later, Bảo Đại would be deposed by his prime minister, Ngô Đình Diệm, creating the Republic of Vietnam.
In August 1954, in support to the French navy and the merchant navy, the U.S. Navy launched Operation Passage to Freedom and sent hundreds of ships, including USS Montague, in order to evacuate non-communist—especially Catholic—Vietnamese refugees from North Vietnam following the July 20, 1954, armistice and partition of Vietnam.
In August Operation Passage to Freedom began, consisting of the evacuation of Catholic and loyalist Vietnamese civilians from communist North Vietnamese persecution.