Battle of Bang Bo ( Zhennan Pass ) The Battle of Bang Bo , known in China as the battle of Zhennan Pass ( Chinese : 鎮南關之役 ) , was an important Chinese victory during the Sino - French War ( August 1884 – April 1885 ) . The battle , fought on 23 and 24 March 1885 on the Tonkin - Guangxi border , saw the defeat of 1 , 500 soldiers of General François de Négrier ' s 2nd Brigade of the Tonkin Expeditionary Corps by a Chinese army under the command of the Guangxi military commissioner Pan Dingxin ( ) . The battle set the scene for the French Retreat from Lang Son on 28 March and the conclusion of the Sino - French War in early April in circumstances of considerable embarrassment for France . The Tonkin military stalemate , March 1885 . On 17 February 1885 General Louis Brière de l ' Isle , the general - in - chief of the Tonkin Expeditionary Corps , left Lang Son with Lieutenant - Colonel Laurent Giovanninelli ' s 1st Brigade to relieve the Siege of Tuyen Quang . On 3 March , at the Battle of Hoa Moc , Giovanninelli ' s men broke through a formidable Chinese blocking position and relieved the siege . Before his departure Brière de l ' Isle ordered General François de Négrier , who remained at Lang Son with the 2nd Brigade , to press on towards the Chinese border and expel the battered remnants of the Guangxi Army from Tonkinese soil . After resupplying the 2nd Brigade with food and ammunition , de Négrier defeated the Guangxi Army at the Battle of Dong Dang on 23 February and cleared it from Tonkinese territory . For good measure , the French crossed briefly into Guangxi province and blew up the ' Gate of China ' , an elaborate Chinese customs building on the Tonkin - Guangxi border . They were not strong enough to exploit this victory , however , and the 2nd Brigade returned to Lang Son at the end of February . By early March , in the wake of the French victories at Hoa Moc and Dong Dang , the military situation in Tonkin had reached a temporary stalemate . Giovanninelli ' s 1st Brigade faced Tang Jingsong ' s Yunnan Army around Hung Hoa and Tuyen Quang , while de Négrier ' s 2nd Brigade at Lang Son faced Pan Dingxin ' s Guangxi Army . Neither Chinese army had any realistic prospect of launching an offensive for several weeks , while the two French brigades that had jointly captured Lang Son in February were not strong enough to inflict a decisive defeat on either Chinese army separately . Brière de l ' Isle and de Négrier examined the possibility of crossing into Guangxi with the 2nd Brigade to capture the major Chinese military depot at Longzhou , but on 17 March Brière de l ' Isle advised the army ministry in Paris that such an operation was beyond their strength . Substantial French reinforcements reached Tonkin in the middle of March , giving Brière de l ' Isle a brief opportunity to break the stalemate . He moved the bulk of the reinforcements to Hung Hoa to reinforce the 1st Brigade , intending to attack the Yunnan Army and drive it back beyond Yen Bay . While he and Giovanninelli drew up plans for a western offensive , he ordered de Négrier to keep the Chinese in respect around Lang Son . Meanwhile , behind the Chinese border , the Guangxi Army was also building up its strength . The French , whose Vietnamese spies in Longzhou had been conscientiously counting the company flags of every Chinese battalion that passed through the town , estimated on 17 March that they were facing a Chinese force of 40 , 000 men . This was an exaggeration , based on the assumption that each Chinese company was at full strength . In fact most of the Chinese commands were considerably understrength with 300 to 400 men , and the strength of the Guangxi Army at the Battle of Zhennan Pass was probably around a couple thousand men , while all of Longzhou had 25 , 000 to 30 , 000 men under arms . Even at this lower strength , it fearfully outnumbered the French . French and Chinese forces . By the middle of March nine separate Chinese military commands were massed close up to the Tonkinese border around the enormous entrenched camps of Yen Cua Ai and Bang Bo . There were six main Chinese concentrations . The entrenched camp of Yen Cua Ai was held by ten battalions under the command of Feng Zicai ( 馮子材 ) and a slightly smaller force under the command of Wang Xiaochi ( 王孝祺 ) . These two commands numbered perhaps 7 , 500 men in all . Two to three kilometres behind Yen Cua Ai , around the village of Mufu , lay the commands of Su Yuanchun ( 蘇元春 ) and Chen Jia ( 陳嘉 ) , perhaps 7 , 000 men in all . Fifteen kilometres behind Mufu the commands of Jiang Zonghan ( 蔣宗漢 ) and Fang Yusheng ( 方友升 ) , also 7 , 000 strong , were deployed around the village of Pingxiang ( known to the French from its Vietnamese pronunciation as Binh Thuong ) . The commander of the Guangxi Army , Pan Dingxin ( 潘鼎新 ) , lay at Haicun , 30 kilometres behind Mufu , with 3 , 500 men . Fifty kilometres to the west of Zhennanguan , 3 , 500 men under the command of Wei Gang ( 魏綱 ) were deployed around the village of Aiwa . Finally , fifteen kilometres to the east of Zhennanguan , just inside Tonkin , Wang Debang ( 王德榜 ) occupied the village of Cua Ai with 3 , 500 men . De Négrier ' s 2nd Brigade numbered around 2 , 500 men . The brigade ' s order of battle in March 1885 was as follows : Roussel ' s battery , of Giovanninelli ' s 1st Brigade , was also at Lang Son . The battery had lagged behind during the Lang Son Campaign , and Giovanninelli had left it at Lang Son when he set out with the 1st Brigade to relieve Tuyen Quang . Not all of the 2nd Brigade was stationed at Lang Son and immediately available for action . The four companies of Servière ' s 2nd African Battalion were echeloned between Lang Son and Chu , guarding the vital French supply line up to Lang Son and labouring to improve the miserable paths over which the expeditionary corps had advanced in February into a surfaced wagon road . The battle of Bang Bo , 23 and 24 March 1885 . On 22 March , Chinese forces under the command of Feng Jicai raided the French forward post at Dong Dang , a few kilometres north of Lang Son . The French post , under the command of Lieutenant - Colonel Paul - Gustave Herbinger , was held by " chef de battalion " Diguet ' s 2nd Foreign Legion Battalion , and the legionnaires repelled the Chinese assault without difficulty . De Négrier , who had been forced to bring the bulk of the 2nd Brigade up from Lang Son to support Herbinger , decided to hit back immediately . Hoping to take the Chinese by surprise , he decided to cross the frontier and attack the Guangxi Army in its entrenchments at Bang Bo , near the frontier pass of Zhennanguan . He had no intention of launching a major offensive into Guangxi . His aim , in the military phrase of the day , was simply to ' take some air ' ( " se donner de l ' air " ) around Dong Dang . After giving the Chinese a bloody nose at Bang Bo and clearing them away from the approaches to Dong Dang , he would return to Lang Son with the 2nd Brigade . Leaving " chef de bataillon " Servière to hold Lang Son with a single company of the 2nd African Battalion and Martin and Roussel ' s batteries , and stationing the 23rd Line Battalion at Dong Dang to protect his supply line , he advanced to the Chinese frontier at Zhennanguan on the morning of 23 March with a force of only 1 , 600 men and 10 guns ( the 111th and 143rd Line Battalions , the 2nd and 3rd Legion Battalions and Roperh and de Saxcé ' s batteries ) . Substantial reinforcements for the 2nd Brigade were already on their way up to Lang Son , but de Négrier decided not to wait for them . He judged it more important to attack the Chinese while they were still discouraged by Feng Zicai ' s repulse on 22 March . On 23 and 24 March the 2nd Brigade fought a fierce action with the Guangxi Army near Zhennanguan . This engagement , known as the Battle of Zhennan Pass in China , is normally called Bang Bo in European sources , after the name of a village in the centre of the Chinese position where the fighting was fiercest . The French took a number of outworks on 23 March , and defeated a hesitant Chinese counterattack against their right flank launched by Wang Debang from Cua Ai . On 24 March de Négrier attacked the Guangxi Army ' s main positions around Bang Bo . His plan called for a simultaneous frontal and rear attack on Feng Zicai ' s troops , who were holding a line of trenches in front of Bang Bo known to the French as the ' Long Trench ' . The frontal attack would be delivered by Faure ' s 111th Battalion and the rear attack by Diguet ' s 2nd Legion Battalion and Farret ' s 143rd Battalion . Herbinger , who was instructed to guide Diguet and Farret to their attack positions , led the two battalions in a wide outflanking march in thick fog , and lost his way . De Négrier , unaware that Herbinger had failed to reach his positions , and mistaking a column of Chinese troops moving up to the Long Trench for Herbinger ' s two battalions , ordered " chef de bataillon " Faure ' s 111th Battalion to deliver its planned frontal attack . The men of the 111th laid down their haversacks , formed up , and charged . The battalion came under heavy frontal fire from Feng Zicai ' s infantry and flanking fire from Chinese units on the nearby hills , and lost several company officers within seconds . Two of the four companies of the 111th Battalion reached the trench , but after a short spell of hand - to - hand fighting were thrown back by a Chinese counterattack led personally by Feng Zicai . The senior surviving French company officer , Captain Verdier ( who later wrote a detailed account of the campaign , " La vérité sur la retraite de Lang - Son " , under the pseudonym Jacques Harmant ) , was able to disengage and rally the battalion . The Chinese , intent on beheading the French wounded and plundering the abandoned French haversacks , did not seriously pursue the 111th Battalion , and Verdier was able to withdraw its shredded companies to safety . Among the officers who fell during the 111th Battalion ' s attack on the Long Trench was 2nd Lieutenant Rene Normand , shot in the throat and mortally wounded . Normand had only recently arrived in Tonkin , and had distinguished himself on 10 February 1885 at the engagement at Pho Vy during the Lang Son Campaign . A collection of his letters from Tonkin , including a number of vivid descriptions of the February campaign to capture Lang Son , would be published posthumously in France in 1886 . On the right of the battlefield , the 143rd Battalion and 2nd Legion Battalion went into action several hours later than expected , and captured a Chinese fort . It was the only French success of the day . At 3 p . m . Pan Dingxin , seeing the 111th Battalion in full retreat and Herbinger ' s men exhausted from their exertions , counterattacked along the entire front . Herbinger ' s command was nearly cut off . Captain Gayon ' s company of the 143rd Battalion was surrounded by the Chinese . Captain Patrick Cotter , an Irish officer in Diguet ' s Legion battalion , ignored an order from Herbinger to leave Gayon to his fate and led his Legion company to the rescue . The legionnaires charged and successfully disengaged Gayon ' s men , but Cotter was killed in the attack . Diguet and Farret ' s battalions fell back by echelons , constantly turning and firing to keep the Chinese in respect . Meanwhile , Schoeffer ' s 3rd Legion Battalion , which had been ordered to remain on Tonkinese soil around Dong Dang to protect the flanks of the French column , fought desperately to keep open a line of retreat for the 2nd Brigade . Schoeffer ' s men beat off strong Chinese attacks on both French flanks , enabling the other three infantry battalions and the two artillery batteries to make good their retreat . General de Négrier fought with the French rearguard , setting an example of personal courage , and the Chinese were unable to convert the French retreat into a rout . In the final flurry of action , just before nightfall , Captain Brunet of Schoeffer ' s battalion was shot dead . There were ominous scenes of disorder as the defeated French regrouped after the battle , and de Négrier had to intervene sharply to quell them . As the brigade ' s morale was precarious and ammunition was running short , de Négrier decided to fall back to Lang Son . On the evening of 24 March the brigade marched back to Dong Dang , where it camped for the night . Hungry , exhausted , and shocked by their defeat , many French troops found it difficult to credit what had happened . Sergeant Maury of Diguet ' s 2nd Legion Battalion was overcome by a nervous reaction : The night was very dark . The soldiers marched in complete silence . We felt cheated , ashamed , and angry . We were leaving behind us both victory and many of our friends . From time to time , in low murmurs , we established who was missing . Then we relapsed into the silence of mourning and the bitterness of loss . And so we reached Dong Dang , without being disturbed . We slept in the field hospital huts , after drinking some soup . We were harassed and hungry . We had not eaten all day , and had drunk nothing since morning except a single cup of coffee . In spite of my weariness , I spent a troubled night . My spirits were haunted by the day ' s memories , by images of the fighting and phantasms of our misfortunes . I was shaken with spasms . I trembled as I have never done on the battlefield . I lay down , but was unable to sleep . Casualties . Although the French made a fighting withdrawal from the battlefield and prevented the Chinese from piercing their line , casualties in the 2nd Brigade during the two - day battle were relatively heavy : 74 killed ( including 7 officers ) and 213 wounded ( including 6 officers ) . Most of these casualties ( 70 killed and 188 wounded ) were suffered on 24 March . The heaviest casualties were suffered by the 111th Battalion ( 31 killed and 58 wounded ) and the 2nd Legion Battalion ( 12 killed and 68 wounded ) . There were also appreciable casualties in the 143rd Battalion ( 17 killed and 48 wounded ) and the 3rd Legion Battalion ( 12 killed and 34 wounded ) . The dead and mortally wounded officers included Captain Mailhat , Doctor Raynaud , Lieutenant Canin and 2nd Lieutenant Normand of the 111th Battalion , Lieutenant Thébaut of the 143rd Battalion , Captain Cotter of Diguet ' s Legion battalion and Captain Brunet of Schoeffer ' s Legion battalion . The wounded officers included " chef de bataillon " Tonnot of the Tonkinese Rifles , Lieutenant de Colomb of the 111th Battalion , Lieutenant Mangin and 2nd Lieutenant Bruneau of the 143rd Battalion and Lieutenant Durillon and 2nd Lieutenant Comignan of Diguet ' s battalion . Lieutenant Mangin died several days after the battle in Lang Son , from shock following an operation to amputate a wounded limb . Chinese estimates of French casualties during the two - day battle amounted to over 1 , 100 dead . Significance . The French defeat at Bang Bo on 24 March 1885 shook the nerve of several French politicians who had earlier supported France ' s war against China . More importantly , it convinced Lieutenant - Colonel Paul - Gustave Herbinger , de Négrier ' s second - in - command , that the 2nd Brigade was dangerously isolated at Lang Son . On 28 March de Négrier was seriously wounded in the battle of Ky Lua , in which the Tonkin Expeditionary Corps defeated an attack by the Guangxi Army on the defences of Lang Son . Herbinger assumed command of the 2nd Brigade , and immediately ordered a retreat to Kep and Chu . The battle of Bang Bo therefore paved the way for the Retreat from Lang Son and the collapse of Jules Ferry ' s administration on 30 March in the Tonkin Affair . The battle , before the war ended due to negotiations , made China appear seem to be almost victorious in the entire war in light of the French defeats at Zhennan and Langson