Battle of Phủ Hoài The Battle of Phu Hoai ( 15 August 1883 ) was an indecisive engagement between the Tonkin Expeditionary Corps and Liu Yongfu ' s Black Flag Army during the early months of the Tonkin campaign ( 1883 – 1886 ) . The battle took place during the period of increasing tension between France and China that eventually culminated in the Sino - French War ( August 1884 – April 1885 ) . Background . The Tonkin campaign is conventionally considered to have begun in June 1883 , with the decision by the French government to despatch reinforcements to Tonkin to avenge the defeat and death of Henri Rivière at the hands of Liu Yongfu ' s Black Flag Army at the Battle of Paper Bridge on 19 May 1883 . These reinforcements were organised into a Tonkin Expeditionary Corps , which was placed under the command of " général de brigade " Alexandre - Eugène Bouët ( 1833 – 87 ) , the highest - ranking marine infantry officer available in the French colony of Cochinchina . The French position in Tonkin on Bouët ' s arrival in early June 1883 was extremely precarious . The French had only small garrisons in Hanoi , Haiphong and Nam Dinh , isolated posts at Hon Gai and at Qui Nhon in Annam , and little immediate prospect of taking the offensive against Liu Yongfu ' s Black Flags and Prince Hoang Ke Viem ' s Vietnamese . During June the French dug in behind their defences and beat off half - hearted Vietnamese demonstrations against Hanoi and Nam Dinh . The early arrival of reinforcements from France and New Caledonia and the recruitment of Cochinchinese and Tonkinese auxiliary formations allowed Bouët to hit back at his tormentors . On 19 July " chef de bataillon " Pierre de Badens , the French " commandant supérieur " at Nam Dinh , attacked and defeated Prince Hoang Ke Viem ' s besieging Vietnamese army , effectively relieving Vietnamese pressure on Nam Dinh . The arrival of Admiral Amédée Courbet in Along Bay in July 1883 with substantial naval reinforcements further strengthened the French position in Tonkin . Although the French were now in a position to consider taking the offensive against Liu Yongfu , they realised that military action against the Black Flag Army had to be accompanied by a political settlement with the Vietnamese court at Hue , if necessary by coercion , that recognised a French protectorate in Tonkin . On 30 July 1883 Admiral Courbet , General Bouët and Jules Harmand , the recently appointed French civil commissioner - general for Tonkin , held a council of war at Haiphong . The three men agreed that Bouët should launch an offensive against the Black Flag Army in its positions around Phu Hoai on the Day River as soon as possible . They also noted that the Court of Hue was covertly aiding and abetting Liu Yongfu ' s Black Flag Army , and that Prince Hoang was still in arms against the French at Nam Dinh . They therefore decided , largely on Harmand ' s urging , to recommend to the French government a strike against the Vietnamese defences of Hue , followed by an ultimatum requiring the Vietnamese to accept a French protectorate over Tonkin or face immediate attack . The proposal was approved by the navy ministry on 11 August , and on 20 August , in the Battle of Thuan An , the French stormed the forts at the mouth of the Hue River , allowing them to attack Hue directly if they chose . The Vietnamese asked for an armistice , and on 25 August Harmand dictated the Treaty of Hue to the cowed Vietnamese court . The Vietnamese recognised 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 . While Harmand and Courbet were entrenching the French protectorate at Hue , General Bouët attempted to carry out his part of the programme settled at the Haiphong conference of 30 July . On 15 August 1883 , Bouët attacked Liu Yongfu ' s Black Flag Army in its strong defensive positions in front of the Day River . Forces involved . General Bouët committed 2 , 500 French and Vietnamese soldiers to the attack . The French force consisted of three marine infantry battalions ( " chefs de bataillon " Chevallier , Lafont and Roux ) , three marine artillery batteries ( Captains Isoir , Dupont and Roussel ) , four companies of Cochinchinese riflemen and around 450 Yellow Flag auxiliaries . The attackers advanced in three separate columns . The left column , under the command of Lieutenant - Colonel Révillon , consisted of a marine infantry battalion , a supporting company of Cochinchinese riflemen and two artillery sections . It was accompanied by the Yellow Flag auxiliary battalion . The centre column , under the command of Bouët ' s chief of staff , " chef de bataillon " Paul Coronnat , consisted of a marine infantry battalion with a supporting company of Cochinchinese riflemen and a marine artillery battery . The right column , under the command of Colonel Bichot , also included a marine infantry battalion , a supporting Cochinchinese rifle company and a marine artillery battery . Bichot ' s column , whose right flank lay on the Red River , was supported by six French gunboats ( " Pluvier " , " Léopard " , " Fanfare " , " Éclair " , " Mousqueton " and " Trombe " ) from the Tonkin Flotilla , under the command of " capitaine de vaisseau " Morel - Beaulieu . Bouët himself marched behind Révillon ' s column with a small general reserve . The Black Flag Army seems to have fielded around 3 , 000 men . Although Liu Yongfu ' s forces did not substantially outnumber the French , they had built two lines of field fortifications to block the road to Son Tay . The first , outpost , line ran from the village of Cau Giay near Paper Bridge , the scene of Rivière ' s defeat and death on 19 May , to the Pagoda of the Four Columns ( Quatre Colonnes ) on the Red River . The main line of defence ran behind it , taking in the villages of Phu Hoai , Noi and Hong . The battle . Révillon ' s left column unsuccessfully attacked the right of the Black Flag line and was counterattacked in its turn by Liu Yongfu and the bulk of the Black Flag Army . As ammunition was running short the French fell back towards Paper Bridge . Their retreat nearly turned into a rout , as the Vietnamese coolies with the column streamed to the rear in panic , blocking the dyke paths along which fresh supplies of ammunition were being brought forward . However , Chevallier ' s marine infantry battalion , firing from sheltered positions in the village of Vong , successfully covered the French withdrawal , inflicting heavy casualties on Black Flag units that left their defences and ventured out into the open . Towards nightfall Bouët committed his reserve , enabling Révillon to stabilise his line . Having heard no news of the progress of the other two columns , Bouët ordered Révillon ' s column to return to Hanoi the same evening . The reason that Liu Yongfu was able to make such a powerful counterattack against Révillon ' s column was because the other two French columns failed to put serious pressure on the enemy . Coronnat ' s centre column failed to make contact with the Black Flags at all , while Bichot ' s right column succeeded in capturing the village of Trem but was then held up in front of the Black Flag defences at Quatre Colonnes . On 16 August Bichot advanced to attack Quatre Colonnes , only to find that the Black Flags had abandoned their positions during the night . The battle had been fought in pouring rain , and during the night of 15 August the Red River burst its banks and began to flood the plains between Hanoi and Phu Hoai . The flooding effectively brought the battle to an end . Neither Coronnat nor Bichot was able to make any further headway on 16 August . Coronnat ' s column returned to Hanoi , while Bichot contented himself with occupying Quatre Colonnes and bringing back to Hanoi a number of cannon abandoned by the Black Flags in their retreat . The French would later claim that the floods had prevented them from inflicting a major defeat upon Liu Yongfu . In fact , the flooding was a disaster for the Black Flag Army . Liu Yongfu had to abandon his entrenchments in front of the Day River and fall back behind the river , leaving behind all his material and all his wounded . French casualties in the Battle of Phu Hoai were 17 dead ( including 2 officers ) and 62 wounded . The French estimated Black Flag casualties at around 300 dead and 800 wounded . Significance . Although the French severely mauled the Black Flag Army during the battle and suffered relatively low casualties in return , their failure to win a clear victory against Liu Yongfu was widely noted . Although the atrocious weather was the most important reason for the failure of Bouët ' s attack , poor French command decisions and the extremely stubborn defence put up by the Black Flags were also contributory factors . The indecisive outcome of the battle discouraged many ordinary Tonkinese from supporting the French against the Black Flags , and in the eyes of the world was tantamount to a French defeat .