Beginning with the punitive expedition against the Vietnamese Empire for the persecution of Catholic missionaries in 1858, the French army found itself, after 50 years, controlling an area of 750,000 square kilometers in Southeast Asia. It took dozens of years for the French to conquer all the territories of the future so-called Indo-Chinese Union, which the French created in 1857 to include the colony of Cochin China, and the four protectorates of Annam, Tonkin, Cambodia, and Laos. French missionaries had been active in Vietnam since the 17th century, and by the middle of the 19th century, a community of 600,000 Roman Catholic converts existed in Annam and Tonkin.
During the 1840s, persecution or harassment of Catholic missionaries in Vietnam evoked only sporadic or unofficial French response. Emperor Thu Duc continued the policies of his predecessors, shutting Vietnam off from the outside world and refusing all efforts to modernize the country. He was confident that France was too involved with the chaos that existed in Europe after 1848 to respond, and in 1857 approved the execution of two Spanish Catholic missionaries. This was neither the first nor the last such incident. But this event coincided with the Second Opium War, and France and Britain had just recently dispatched a joint military expedition force to the Far East in order to attack China.
France used these forces to subsequently intervene in Indochina. In November 1857, Napoleon III of France ordered Admiral Charles Rigaud de Genoilly to lead a punitive expedition against Vietnam. On 1 September 1858, with 14 French gunships, 3,000 men and 300 Filipino troops provided by the Spanish, he attacked the port of Da Nang and captured the town in the same day.
The Europeans anticipated an easy victory, but the campaign did not go as planned. The Vietnamese Christian community did not rise in support of France, and the well-organized Vietnamese military resistance was more formidable than expected. The French and Spanish found themselves in no position to progress further inland after capturing the city and were pinned down in a long siege by a Vietnamese army under the command of Nguyen Tri Phuong. Realizing that the French garrison at Da Nang was not to achieve a strategic success shortly, Rigaud de Genouilly decided to attack Saigon, a city with considerable strategic significance and a source of food for the Vietnamese army.
He left in Da Nang a small French garrison and two gunboats to resist against the Vietnamese siege. On 17 February 1859, after breaking the river defenses and destroying a series of forts and stockades along the Saigon River, the French and Spanish captured Saigon. The Allies lacked the manpower to hold the citadel and on 8 March 1859 demolished it and set fire to the rice granaries. The Franco-Spanish garrison, of around 1,000 men was placed under siege by a Vietnamese army of about 10,000 men.
Due to the resumption of fighting in China during the Second Opium War, the French had to divert most of their troops in the region to China. Realizing that they could hold only either Saigon or Da Nang, the French evacuated the garrison of Da Nang in March 1860. Emperor Thu Duc was encouraged by this victory to continue the war refusing to negotiate a peace treaty with the French, who were ready to retreat from Vietnam without making any territorial gains if the protection of the Catholic faith would have been guaranteed. In early 1861, the war with China ended and the French were now free to return to Cochinchina and resume the campaign around Saigon.
A naval contingent of 70 ships and 3,500 soldiers were transferred from northern China to Saigon. These reinforcements eventually provided the Allies with troops for tactical maneuvers at Saigon. On 24 and 25 February 1861, the French and Spanish successfully assaulted the Vietnamese siege lines, defeating Marshal Nguyen Tri Phung in the Battle of Ky Hoa.
The victory at Ky Hoa allowed the French and Spanish to regain the operational initiative. My Tho was occupied by the French on 12 April 1861. Bien Hoa was captured on the 16th of December 1861 and Vinh Long on the 22nd of March 1862. After losing these cities in April 1862, two dukes announced that he wished to make The Treaty of Saigon was signed on 5 June 1862. Vietnam accepted to legalize the free practice of the Catholic faith within its territory, to cede the provinces of Bien Hoa, Gia Dinh and Dinh Tung to France, to allow the French to trade and travel freely along the Mekong River, and to pay an indemnity of $1 million to France and Spain over a 10-year period. The French placed all acquired territories under the administration of the Marine Ministry, thereby establishing the colony of Cochin China with its capital Saigon.
In 1863, the Cambodian king Norodom had requested the establishment of a French protectorate over his country. In 1867, Siam, the modern Thailand, renounced its serenity over Cambodia and officially recognized the 1863 French protectorate on Cambodia in exchange for the control of Battambang and Siem Reap provinces, which officially became part of Thailand. Between 20-24 June 1867, the French admiral Pierre de la Grandiere occupied three additional provinces to the west of Cochin, China Châu Đốc, A Tiên and Vinh Long.
Phan Thanh Giang, the governor of these provinces, chose to avoid armed resistance, to avoid bloodshed and then committed suicide. With these three additions, all of southern Vietnam and the Mekong Delta fell under French control. In 1873, Francis Garnier was put in charge of an expedition to Tonkin, with a mission of protecting French interests there.
Garnier disembarked in Hanoi on 3 November 1873, but negotiations were not for coming. On 20 November, Garnier made an assault of the Hanoi citadel and pacified the delta with nine officers, 175 men. and two gunboats.
The Black Flag Army, a large Chinese bandit group led by Liu Yongfu, resisted the French intrusion, entering into a guerrilla campaign that led to the killing of Garnier on 21 December 1873. In March 1882, Captain Henri Rivière again visited Hanoi with three gunboats and 700 men in order to obtain a trade agreement. Following some provocations, Rivière captured Hanoi in in April 1882. Again, the Black Flags counterattacked and Rivière was killed in May 1883 in the Battle of Paperbridge, leading to a huge movement in favor of a massive baron intervention in France. Credits were voted for and a large force of 4,000 men and 29 warships was sent. Meanwhile, a succession crisis followed the death of two dukes on 19 July 1883, as the regent Tonta Tuyet orchestrated the murders of three emperors in a year.
This allowed the French to easily take control of the country and its monarchy. All emperors after Don Khan were chosen by the French and only ruled symbolically. Although the French were now in a position to consider taking the offensive against the Black Flag Army, they realized that the Vietnamese court of Hue was covertly supporting and aiding the bandits. They decided to destroy the defenses of the Vietnamese capital of Hue and then to send an ultimatum requiring the Vietnamese to accept a French protectorate over Tonkin or face immediate attack.
On the 18th of August 1883, several French warships bombarded the Toan Anh forts at the entrance of the Hue river. On the 20th of August, in the Battle of Toan Anh, two companies of French marine infantry and the landing companies of three French warships went ashore and stormed the forts under heavy fire. The French were now able to attack Hue directly if they chose. The Vietnamese asked for an armistice and on the 25th of August signed the Treaty of Hue.
The Vietnamese recognized the legitimacy of the French occupation of Cochinchina, accepted a French protectorate both for Annam and Tonkin, and promised to withdraw their troops from Tonkin. Vietnam, its royal house, and its court survived, but under French direction. The next objective of the French was to take full control of the Tonkin. In October 1883, Admiral Amedee Corbet was placed in command of the Tonkin Expeditionary Corps. In December 1883, he led the Sontag Campaign against the Black Flags.
French casualties were heavy, but the Black Flags were very weakened as a result of the campaign. The Bac Ninh Campaign in March 1884 was one of a series of clashes, between French and Chinese forces in Tonkin. The campaign, which lasted from 6 to 24 March, resulted in the French capture of Bac Ninh and the complete defeat of China's Guansi army.
China, the traditional overlord of Vietnam, kept contesting French influence in the area and was supporting Annam as well as the Black Flags on its territory at the frontier with Tonkin. Although the Tianjin Accord had been signed between France and China on 11 May 1884, promising Chinese evacuation from the region, the Chinese army was not able to from Tonkin, military confrontations continued as in the Bakli ambush in June 1884. These tensions led to the Sino-French War in 1884-1885, which ultimately forced China to abandon its historic to suzerainty over Vietnam and confirmed the French protectorate over both Annam and Tonkin. French continued to consolidate their presence in northern Vietnam, and the total number of French soldiers in Tonkin increased to 35,000 in the summer of 1885. Tonkin was considered to be pacified in April 1886. In 1885, a French consulate was established in the kingdom of Luang Prabang, which was a vassal kingdom to Siam. Siam, led by King Jula Longkorn, soon feared that France was planning to annex Luang Prabang and signed a treaty with the French on 7 May 1886, which recognized Siam's suzerainty over the Lao kingdoms.
In 1888, the Black Flag Army declared war on Siam and its vassal state of Luang Prabang by sacking its capital. French forces later intervened and evacuated the Lao royal family to safety. Additional French troops were deployed to the island of Luang Prabang and the island from Hanoi later arrived to expel the Black Flags from Luang Prabang.
Following his return to the city, King Ong Kam requested a French protectorate over his kingdom. Both sides accepted on 27 March 1889 to make Luang Prabang a French protectorate despite the Siamese protest. France and Siam went to war in 1893, and the kingdom was forced to recognize French control over the eastern side of the Mekong River.
acceptance of the ultimatum to cede the lands east of the Mekong, including its islands, the Protectorate of Laos was officially established and the administrative capital moved from Luang Prabang to Vientiane. However, Luang Prabang remained the seat of the royal family, whose power was reduced to figureheads, while the actual power was transferred over to French officials. In January 1896, France and the United Kingdom signed an accord recognizing the border between French Laos and Vientiane. British Burma.
In 1902, the treaty with Siam forced the kingdom to also surrender lands on the western side of the Mekong River. These lands now formed the province of Sainiabuli and the western half of Champasak province. The French, however, continued to pressure Siam, and in 1906-1907, Siam had to concede to the French the territory of western Cambodia. French plans to expand their territories in Indochina ended in 1907 after the French after Siam began cooperating with the British to control French expansion in the region, which the British Empire feared would have eventually led to a French annexation of Siam, overthrowing the region's balance of power.