In what is referred to as the French Takeover of Vietnam, military activity of France in Vietnam commenced in 1847 when the Danang harbor was attacked by the French navy in reaction to Emperor Thieu Tri's repression of Catholic missionaries. According to Jacques “Saigon was seized in early 1859 and, in 1862, Emperor Tu Duc signed a treaty that gave the French the three eastern provinces of Cochin China” but for the following four decades the colonial venture of French in Indochina was carried out chaotically and with lack of a specific preconceived plan. It time after time faltered and, most of the times, only the careless adventures of a few nonconformists kept it moving. The subsequent saga in the French colonization commenced in 1872 when a merchant known as Jean Dupuis, in quest of salt and weapons supply to a Yunnan’s general through the Red River, took over the Hanoi Citadel.
Successors of Gia Long's cared less for Christianity or Europeans. These two had come to Vietnam with the objective of reunification. Unidentified number of Christians and seven missionaries were executed in the early 19try century. The remaining missionaries and various advisors of France were expelled. France cautioned the emperors to not execute nor expel their Christian subjects, and in 1847 in their attempt to show that they meant business French bombarded the harbor of Da Nang (described as Tourane by the French) (Windrow,1998. pp. 11).
The next emperor of Vietnam, Tu Duc (1848-83), gave a response by giving rewards for the murder of Europeans and by branding and banishing any indigenous priest he could come across. The Catholic Church asked for a military mission against Vietnam, but involvement was deferred for over a decade while the French were busy with various happenings in Europe like the rise of Napoleon III, the 1848 revolutions, and the Crimean War. The pronouncement to have Vietnam invaded was made in 1857 by Napoleon III. Following some delays, a 5,000 men and 14 ships taskforce arrived in Da Nang in the year 1858 (Smedberg, 2008, p.88). It took them only a day to take over the town, but could not make any further progress due to lack of the essential shallow-draft boats which could enable them to go up the Perfume River to Hue. They therefore could not threaten the capital of Vietnam. More badly, there were no reinforcements that came on time for they went to reinforce the British in the second opium War with china. Therefore the anticipated anti-government uprisings by Vietnamese Catholics were unsuccessful. Above all that, French battle was completely weakened by tropical diseases infetions and when the rainy season came in October, the army was totally immobilized.
The French commander, Adm. Rigault Genouilly, made a decision to leave Da Nang and hit the south. It is in this case that he hit the central point; he seized Saigon, the major city in the rice-growing Mekong delta expanse. Tu Duc could still not admit defeat, and almost immediately Saigon was under siege by the large number of Vietnamese forces. The state of affairs continued being a stalemate until the year 1861, when the French garrison got reinforcements from army returning from the Chinese mission, together with some Spanish troops who were returning from Manila. Now the France and Spanish forces took on the offensive, organizing themselves to seize three major provinces of the six provinces in the Mekong delta. Smedberg, 2008 argues that, due to lack of the capacity to oppose the western modern military technology, Tu Duc gave in, and signed away the French seized provinces in the treaty that followed. At this point, the Spanish no longer had any interest in Vietnam and they withdrew, but French were left to further their interests. A year later, in 1863, a French officer paid a visit to the king of Cambodia and by force made him at gunpoint to sign a pact that relocated the vassalage of Cambodia's from Siam to France. In the year 1867 the Saigon governor took possession of the remaining part of the Mekong delta for France, supposedly in prevention of the Vietnamese meddling in the affairs of Cambodia (Smedberg, 2008, p.88).
For sometimes French were optimistic that the Mekong could be a useful trade route to the southwest China. They anticipated that this route could enable them bring trade goods to millions of prospective customers. It is at this time that explorer Francis Garnier sailed up the river in 1866 to 1868, and reported back later that navigation in the river was only possible up to Laos. However, the Red River, was only proper for commercial traffic, and so the French turned their attention northward to Tonkin.
Jean Dupuis was the first merchant to try the Red River route. In his first atte3mpt he transported a consignment of arms from China to Vietnam in the year 1873. On his way back he attempted to rake a cargo of salt back to china but he was arrested in Hanoi for an attempt to go against the government's monopoly of salt. After the arrest Garnier was sent to Hanoi in company of other 60 men to go and rescue Dupuis; once he was able to do so, he took over the fortress at Hanoi and attempted to seize the whole of Tonkin for France. It did not take long before Garnier died while in a battle with thhe Black Flags, a gang of bandits from china and Vietnam. This marked the end of the campaign towards capturing the north.
France, which had only just suffered a devastating defeat (the Franco-Prussian War of the year 1870 to 1871), was reluctant to send to Saigon any more manpower or money that was necessary for new conquests. The Paris government ant colonial section affirmed that the revival of France should take priority over any other matter for the time being. It took France ten years of speedy economic growth before she was set to come up with the tricolor over more colonies. In April of 1882 an army of 250 men were sent to Hanoi under the leadership of Captain Henri Riviere, to officially repress the Black Flags, who had become so strong and dominated most of Tonkin by that time (Smedberg, 2008, p.88).
When Riviere faced the same circumstances as Garnier, the Chamber of Deputies of France without more ado voted to enforce French rule over Tonkin, irrespective of the cost that would be involved. In august 1883, a stronger expeditionary force was relocated to the Red River delta, while Hue was bombarded by the French fleet, where, strange to the French government, Emperor Tu Duc had passed away only a few weeks before. The court mandarins swiftly submitted the entire country to the French. This was to mark the end of the fight, but a moment before he passed away Tu Duc had come up with an anti-French agreement with China, in upshot using Vietnam's oldest rival to get rid of her latest enemy. A fresh war started, and this time china was in support of Vietnam. The Chinese were so smart on land but in the year 1885 her fleet seized a number of seaports on the coast of china. China was forced to move out of Vietnam if they were to get back their ports. However, Various Vietnamese guerrillas sustained their French resistance before they were completely suppressed at the turn of the century. The final step taken by French in her expansion was the taking over of Laos from Siam in the year 1893, and later on two other pieces of Siamese territory in the year 1904 and 1907 respectively (Duiker, 1976).
It is therefore clear that France colonized Vietnam for the reason that it had a growing interest in the region ever since the commencement of the Nguyen Dynasty in the early on 1800's. The founding Nguyen Emperor, Gia Long, and the following four heirs were strongly opposed to the involvement of French in Vietnam. The persecution of catholic missionaries by Vietnam was the justification that France used to attack and take up Vietnam, Laos and Cambodia to come up with a French colony that they called Indochina.