Capture of Biên Hòa The Capture of Bien Hoa ( Vietnamese : Biên Hòa ) on 16 December 1861 was an important allied victory in the Cochinchina campaign ( 1858 – 62 ) . This campaign , fought between the French and the Spanish on the one side and the Vietnamese on the other , began as a limited punitive expedition and ended as a French war of conquest . The war concluded with the establishment of the French colony of Cochinchina , a development that inaugurated nearly a century of French colonial dominance in Vietnam . Background . After early French victories at Tourane and Saigon , the Cochinchina campaign reached a point of equilibrium with the French and their Spanish allies besieged in Saigon , which had been captured by a Franco - Spanish expedition under the command of Admiral Charles Rigault de Genouilly on 17 February 1859 . The arrival of massive reinforcements from the French expeditionary corps in China in 1860 allowed the French to regain the initiative . On 24 and 25 February 1861 Admiral Léonard Charner relieved the Siege of Saigon by defeating the besieging Vietnamese army in the battle of Ky Hoa . He followed up this victory with the Capture of My Tho ( 12 April 1861 ) . Charner had been sent out to the Far East for the war with China , and had not expected to be required to fight a campaign in Cochinchina as well . Believing that he had broken Vietnamese resistance with his victories at Ky Hoa and My Tho , he asked to return to France in the summer of 1861 . Rear Admiral Louis - Adolphe Bonard ( 1805 – 67 ) , appointed as his successor by an imperial decree of 8 August 1861 , arrived in Saigon on 27 November and assumed his duties on 30 November . Bonard ' s arrival coincided with an upsurge in Vietnamese guerilla activity against the French fomented by the government at Hue , which placed a bounty on the heads of both Frenchmen and Vietnamese in their service . Bands of insurgents attacked Tay Ninh and Tran Bang , and in one particularly galling incident the French lost one of their small warships . A band of Vietnamese mounted a hit - and - run attack on the French lorcha " Espérance " during the absence of her captain , " enseigne de vaisseau " Parfait , and lured the French vessel into an ambush . Her crew of 17 Frenchmen and Filipinos were overpowered and killed , and the insurgents burned the vessel . Bonard decided that an exemplary reprisal was required . A fortnight after his arrival in Saigon , after receiving an unsatisfactory response to an ultimatum he had sent to the Vietnamese governor Nguyen Ba Nghi , he mounted a major campaign to occupy the province of Bien Hoa . The capture . The following account of the capture of Bien Hoa was given by the French historian A . Thomazi : " The Annamese had established defence works on all the routes leading to Bien Hoa . They had built an entrenched camp held by 3 , 000 men at My Hoa , midway between Bien Hoa and Saigon , and obstructed the course of the Donnai with nine solid barrages and a stockade . The admiral decided to attack simultaneously by land and water . He ordered the detached posts to remain on the defensive and to concentrate all disposable forces before Saigon . All being ready , and an ultimatum issued on 13 December going unanswered , the columns set off at daybreak on 14 December . The first column , commanded by " chef de bataillon " Comte and consisting of two companies of " chasseurs à pied " , 100 Spaniards and 50 horsemen with four mortars , made for Go Cong , which it captured at 7 . 30 a . m . A second column , consisting of 100 Spaniards and a battalion of marine infantry with two cannon , under the orders of Lieutenant - Colonel Domenech Diego , placed itself before the camp of My Hao . At the same time " capitaine de vaisseau " Lebris , with two companies of sailors , advanced on the Donnai , taking in reverse the batteries on the right bank . Finally a flotilla of armed launches , having followed the creeks as far as Rach Go Cong , cannonnaded the works which were also bombarding the gunboats anchored in the Donnai under the orders of " lieutenant de vaisseau " Harel of " Avalanche " . The forts replied energetically , and the gunboat " Alarme " was hit by 54 balls and had her main mast nearly destroyed . But once the defenders saw themselves threatened by a land attack , they hastily evacuated the forts , one of which blew up and the others were occupied . The sailors toiled throughout the night to demolish the barrages , while the naval hydrographer Manen sounded the passes . The first obstacles having been destroyed , the two infantry columns joined hands in front of the camp of My Hoa on 15 December . The marine infantry attacked the enemy ’ s centre , while the chasseurs menaced his right and the Spaniards his left , and the cavalry made a turning movement to cut off his retreat . The Annamese panicked and took to flight . Admiral Bonard , aboard the dispatch vessel " Ondine " , ascended the river and exchanged cannon shots with the citadel . On 16 December the troops crossed the Donnai and occupied Bien Hoa , which the Annamese soldiers had evacuated , but not before burning alive numerous Christian prisoners . We took there 48 cannons and 15 armed junks . The operation cost us only 2 men dead and several wounded . "