Capture of Vĩnh Long The Capture of Vinh Long ( Vietnamese : Vĩnh Long ) on 22 March 1862 was the last major allied victory of 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 . The Vinh Long campaign was undertaken by the French and Spanish as a reprisal for Vietnamese guerilla attacks in February and March 1862 on French troops and gunboats in the vicinity of My Tho . French marching columns were sniped at on the roads , and on 10 March a French gunboat ( No . 25 ) carrying a company of soldiers blew up shortly after it left My Tho . Fifty - two men were killed or wounded in this incident , and a commission of enquiry found that the explosion was due to sabotage . Convinced that the mandarins of the province of Vinh Long were behind these attacks , Admiral Louis - Adolphe Bonard , the French commander - in - chief , decided to capture the town of Vinh Long with a flotilla of despatch vessels and gunboats and a joint Franco - Spanish landing force . On 20 March 1862 he arrived before the fortress of Vinh Long with the dispatch vessels " Ondine " ( his flagship ) and " Shamrock " , the gunboats " Dragonne " and " Fusée " and seven small gunboats . The landing force , embarked aboard the gunboats , numbered 700 French soldiers and 300 Spanish soldiers , under the orders of Lieutenant - Colonel Reboul of the marine infantry . On 20 March these troops , reinforced by the ships ’ landing companies , were set ashore at Dinh Kao , to the southeast of the citadel . The capture of Vinh Long . The following account of the attack by Reboul ' s French and Spanish troops on Vinh Long was given by Colonel Thomazi , the historian of the French conquest of Indochina : On 22 March they crossed two arroyos under fire and advanced into view of the enemy batteries , which had been fighting a violent artillery duel with the gunboats . During the night , after a seven - hour struggle , all the batteries were occupied , and on the following day we entered the citadel , where we found 68 cannon and considerable quantities of materiel . Mopping - up operations . The Vietnamese defenders of Vinh Long fell back to a fortified earthwork at My Cui , west of My Tho . Admiral Bonard sent two columns under the respective command of " capitaine de vaisseau " Desvaux and Colonel Carlos Palanca y Guttierez to capture My Cui . Desvaux ' s column , which consisted of two companies of Turcos and a detachment drawn from the garrison of Vinh Long , set off from Vinh Long and approached My Cui via Cai Lay . Palanca y Guttierez ' s column , which consisted of 200 Spanish troops , a company of Turcos and a section of artillery , marched directly on My Cui from Vinh Long . The two columns attacked My Cui simultaneously and captured it . " Lieutenant de vaisseau " Vergnes , who was watching the arroyos around My Tho with a detachment of " fusiliers - marins " , intercepted and inflicted a further defeat on the retreating Vietnamese . Vietnamese casualties were heavy , and the allies also captured a large number of weapons . Aftermath . Coming on the heels of earlier allied victories at My Tho ( April 1861 ) and Bien Hoa ( December 1861 ) , the capture of Vinh Long disheartened the Court of Hue , and in April 1862 Tu Duc let it be known that he was willing to make peace .