French Army in World War I During World War I , France was one of the Triple Entente powers allied against the Central Powers . Although fighting occurred worldwide , the bulk of the fighting in Europe occurred in Belgium , Luxembourg , France and Alsace - Lorraine along what came to be known as the Western Front . Specific operational , tactical , and strategic decisions by the high commands on both sides of the conflict led to shifts in organizational capacity , as the French Army tried to respond to day - to - day fighting and long - term strategic and operational agendas . In particular , many problems caused the French high command to re - evaluate standard procedures , revise its command structures , re - equip the army , and develop different tactical approaches . Background . France had been the major power in Europe for most of the Early Modern Era : Louis XIV , in the seventeenth century , and Napoleon I in the nineteenth , had extended French power over most of Europe through skillful diplomacy and military prowess . The Treaty of Vienna in 1815 confirmed France as a European power broker . By the early 1850s , Prussian Chancellor Otto von Bismarck started a system of alliances designed to assert Prussian dominance over Central Europe . Bismarck ' s diplomatic maneuvering , and France ' s maladroit response to such crises as the Ems Dispatch and the Hohenzollern Candidature led to the French declaration of war in 1870 . France ' s subsequent defeat in the Franco - Prussian War , including the loss of its army and the capture of its emperor at Sedan , the loss of territory , including Alsace - Lorraine , and the payment of heavy indemnities , left the French seething and placed the reacquisition of lost territory as a primary goal at the end of the 19th century ; the defeat also ended French preeminence in Europe . Following German Unification , Bismarck attempted to isolate France diplomatically by befriending Austria – Hungary , Russia , Britain , and Italy . Sometime after 1870 , the European powers began acquiring settlements in Africa , with colonialism on that continent hitting its peak between 1895 and 1905 . However , colonial disputes were only a minor cause of World War I , as most had been settled by 1914 . Economic rivalry was not only a source for some of the colonial conflicts but also a minor cause for the start of World War I . For France the rivalry was mostly with the rapidly industrializing Germany , which had seized the coal - rich region of Alsace - Lorraine in 1870 , and later struggled with France over mineral - rich Morocco . Another cause of World War I was growing militarism which led to an arms race between the powers . As a result of the arms race , all European powers were ready for war . France was bound by treaty to defend Russia , which was in turn bound by treaty to defend Serbia . Austria – Hungary had declared war on Serbia due to the Black Hand ' s assassination of Archduke Ferdinand , which acted as the immediate cause of the war . France was brought into the war by a German declaration of war on August 3 , 1914 . Organization during the war . In January 1914 , the French Army had 47 division s , composed of 777 , 000 French soldiers and 47 , 000 colonial troops . The French army was organized into 21 regional corps , along with attached cavalry and field artillery . Most of these troops were deployed in the French interior , the bulk of those along the eastern frontier as part of Plan XVII . Fear of war meant another 2 . 9 million men were mobilized in the summer of 1914 , and heavy losses on the Western Front forced France to conscript men up to the age of 45 . In June 1915 , the Allied countries met in the first inter - Allied conference . Britain , France , Belgium , Italy , Serbia , and Russia were all represented , and agreed to coordinate their attacks . However , such attempts were frustrated by strategic enemy maneuvers . By 1918 , towards the end of the war , the composition and structure of the French army had changed . Forty percent of all French soldiers on the Western Front were operating artillery and 850 , 000 of the French troops were infantrymen in 1918 , compared to 1 . 5 million in 1915 . Causes for the drop in infantry include increased machine gun , armored car , and tank usage , as well as the increasing significance of the French air force , the Armée de l ' Air . At the end of the war on November 11 , 1918 , the French had called up 8 , 317 , 000 men , including 475 , 000 colonial troops . France suffered over 4 . 2 million casualties , with 1 . 3 million dead . Commanders in Chief . Joseph Joffre was Commander - in - Chief , a position he had held since 1911 . While serving in this position , Joffre was responsible for development of the Plan XVII blueprint for the invasion of Germany , which proved unsuccessful . Joffre was thought to be the ' Savior of France ' due to his serenity and a refusal to admit defeat , valuable at the beginning of the war , along with his regrouping of retreating allied forces at the Battle of the Marne . Joffre was effectively relieved of his duties on December 13 , 1916 , following the Battle of Verdun and other losses . Due to his popularity , it was not presented to the public as a dismissal when he was promoted to Marshal of France on the same day . Robert Nivelle , who began the war as a regiment al colonel , was appointed Commander - in - Chief . However , after the failure of the Nivelle Offensive in April 1917 , and the French army mutinies , he was removed from his position and given a post in North Africa . On May 15 , 1917 , Philippe Pétain was made Commander - in - Chief , and restored the fighting capability of the French troops by improving front line living conditions , and preferring defensive operations . In the Third Battle of the Aisne , fought in May 1918 , French positions collapsed due to Pétain ' s alien tactic of " tactical defense " , and the consequence for Pétain was subordination to the Supreme Allied Commander Ferdinand Foch . Western Front . Germany marched through neutral Belgium as part of the Schlieffen Plan to invade France , and by August 23 had reached the French border town of Maubeuge , whose true significance lay within its forts . Maubeuge was a major railway junction and was consequently a protected city . It had 15 forts and gun batteries , totaling 435 guns , along with a permanent garrison of 35 , 000 troops , a number enhanced by the British Expeditionary Force . The BEF and the French Fifth Army retreated on August 23 , and the town was besieged by German heavy artillery starting on August 25 . The fortress was surrendered on September 7 by General Fournier , who was later court - martialed , but exonerated , for the capitulation . The Battle of Guise , launched on August 29 , was an attempt by the Fifth Army to capture Guise , they succeeded , but later withdrew on August 30 . This delayed the German Second Army ' s invasion of France , but also hurt Lanrezac ' s already damaged reputation . The First Battle of the Marne was fought between September 6 and September 12 . It started when retreating French forces ( the Fifth and Sixth armies ) , stopped south of the Marne River . Victory seemed close , the First German Army was given orders to surround Paris , unaware the French government had already fled to Bordeaux . The First Battle of the Marne was a French victory , but was a bloody one : 250 , 000 French soldiers died , with similar numbers believed for the Germans , and over 12 , 700 for the British . The German retreat after the First Battle of the Marne halted at the Aisne River , and the Allies soon caught up , starting the First Battle of the Aisne on September 12 . It lasted until September 28 , it was indecisive , partially due to machine gun s beating back infantry sent to capture enemy positions . In the Battle of Le Cateau , fought on August 26 – 27 , the French Sixth Army prevented the British from being outflanked . The first major Allied attack against German forces since the incarnation of trench warfare on the Western Front , the First Battle of Champagne , lasting from December 20 , 1914 , until March 17 , 1915 ; it was a German victory , due in part to their machine gun battalions and the well - entrenched German forces . The indecisive Second Battle of Ypres , from April 22 – May 25 , was the site of the first German chlorine gas attack and the only major German offensive on the Western Front in 1915 . Ypres was devastated after the battle . The Second Battle of Artois , from May 9 – June 18 , the most important part of the Allied spring offensive of 1915 , was successful for the Germans , allowing them to advance rather than retreat as the Allies had planned , and Artois would not be in Allied hands again until 1917 . The Second Battle of Champagne , from September 25 – November 6 , was a general failure , with the French only advancing about , and not capturing the German ' s second line . France suffered over 140 , 000 casualties , while the Germans suffered over 80 , 000 . The Battle of the Somme , fought along a front from north of the Somme River between Arras and Albert . It was fought between July 1 and November 18 and involved over 2 million men . The French suffered 200 , 000 casualties . Little territory was gained , only at the deepest points . Battle of the Frontiers . The Battle of the Frontiers consisted of five offensives , commanded and planned by French Commander - in - Chief Joseph Joffre and German Chief - of - Staff Helmuth von Moltke . It was fought in August 1914 . These five offensives , Mulhouse , Lorraine , Ardennes , Charleroi , and Mons , were launched almost simultaneously . They were the result of the French XVII and the German plans colliding . The Battle of Mulhouse , on August 7 – 10 , 1914 , was envisioned by Joffre to anchor the French recapture of Alsace , but resulted in Joffre holding General Louis Bonneau responsible for its failure and replacing him with General Paul Pau . The Battle of Lorraine , August 14 – 25 , was an indecisive French invasion of that region by General Pau and his ' Army of Alsace ' . The Battle of the Ardennes , fought between August 21 and 23 in the Ardennes forests , was sparked by unsuspecting French and German forces meeting , and resulted in a French defeat , forfeiting to the Germans a source of iron - ore . The Battle of Charleroi , which started on August 20 and ended on August 23 , was a key battle on the Western Front , and a German victory . General Charles Lanrezac ' s retreat probably saved the French Army , but Joffre blamed him for the failure of Plan XVII , even though the withdrawal had been permitted . Race to the Sea . The First Battle of Albert was the first battle in the so - called ' Race to the Sea ' , so - called because the campaign was attempting to reach the English Channel in an effort to outflank the German army . The First Battle of Albert was fought on September 25 – 29 , 1914 , after the First Battle of the Marne and the First Battle of the Aisne . It occurred after both sides realized that a breakthrough was not possible . It was evident that both the French Plan XVII and the German Schlieffen Plan had failed . Both sides then proceeded to attempt to outmaneuver the other , and the battle ended indecisively . The Battle of Arras , which was another attempt on the part of the French to outflank the Germans , was started on October 1 . Despite heavy attacks by three corps from the First , Second , and Seventh armies , the French held on to Arras , albeit losing Lens on October 4 . The Battle of the Yser , fought between October 18 and November 30 , was the northernmost battle in the ' Race to the Sea ' . The battle was a German victory , and fighting continued along the Yser River until the final Allied advance that won the war . The last of the ' Race to the Sea ' battles , the First Battle of Ypres , started on October 19 , marked the formation of a bond between the British and French armies . The battle was an Allied victory and ended , according to France , Britain , and Germany , on November 13 , 22 , or 30 respectively . Battle of Verdun . The Battle of Verdun was the longest of the war , lasting from February 21 , 1916 until December 18 of the same year . The battle started after a plan by German General Erich von Falkenhayn to capture Verdun was executed , but after a few weeks , the battle had become a series of local actions . For the French , the battle signified the strength and fortitude of the French Armed Forces . Many military historians consider Verdun the " most demanding " and the " greatest " battle in history . The German attack on Verdun began with one million troops , led by Crown Prince Wilhelm , facing only about 200 , 000 French soldiers . The following day , the French were forced to withdraw to the second line of trenches , and on February 24 , they were pushed back to the third line , only from Verdun . The newly appointed commander of the Verdun sector , General Philippe Pétain , stated that there would be no more withdrawals , and had every French soldier that was available fighting in the Verdun sector , eventually involving 259 out of 330 infantry regiment s . A single road had remained open for trucks , enabling a continual flow of supplies to the defenders . The German attacking forces were not able to enter the city of Verdun itself and by December 1916 had been forced back beyond the original French trench lines of February . The sector became again a relatively inactive one as the allied focus shifted to the Somme and the Germans adopted a defensive stance . While generally regarded as a tactical victory for the French , the battle had caused massive losses on both sides . French casualties had been higher but the original German objective : of taking Verdun while destroying the defending army through a battle of attrition in a restricted area , had not succeeded . Nivelle Offensive . In October 1916 , troops under Robert Nivelle ' s command captured Douaumont and other Verdun forts , making him a national hero . Nivelle formulated a plan using his " creeping barrage " tactics that would supposedly end the war in 48 hours with only 10 , 000 casualties . War Minister Hubert Lyautey , General Philippe Pétain and Sir [ Douglas Haig ] were all opposed to the plan . After Aristide Briand supported the " Nivelle Offensive " , Lyautey resigned . Starting on April 17 , one million French soldiers were deployed on a front between Royle and Reims . The main action of the Nivelle Offensive , the Second Battle of the Aisne , started on April 16 , 1917 , with the French suffering 40 , 000 casualties on the first day . By the time the battle was over on May 9 , the French had suffered 187 , 000 casualties , while the Germans suffered 168 , 000 . The Allies eventually suffered over 350 , 000 casualties fighting the Nivelle Offensive . As a result of the Second Battle of the Aisne and the Nivelle Offensive , 35 , 000 French troops mutinied starting on April 17 . 68 out of 112 divisions were affected . The mutinies ended on June 30 , and contributed to Nivelle ' s replacement by Pétain . Mutinies . In the spring of 1917 , after the failed Nivelle Offensive , there was a series of mutinies in the French army . The mutinies started on April 17 , the day after the failed Nivelle Offensive , and ended on June 30 . Over 35 , 000 soldiers were involved with 68 out of 112 division s affected , but fewer than 3 , 000 men were punished . Following a series of court - martials , there were 49 documented executions and 2 , 878 sentences to penal servitude with hard labour . Of the 68 divisions affected by mutinies , 5 had been “ profoundly affected ” ’ 6 had been “ very seriously affected ” , 15 had been “ seriously affected ” , 25 were affected by “ repeated incidents ” and 17 had been affected by “ one incident only ” , according to statistics compiled by French military historian Guy Pedroncini . Mutinies began in April 1917 failure of the Second Battle of the Aisne , the main action in the Nivelle Offensive . They involved units from nearly half of the French infantry divisions stationed on the western front . The mutinies were kept secret at the time , and their full extent and intensity were not revealed for a half century . The more serious episodes involved only a few units ; the mutinies did not threaten complete military collapse , but did make the high command reluctant to call another offensive . The popular cry was to wait for the arrival of millions of fresh American troops . The mutinous soldiers were motivated by despair , not by politics or pacifism . They feared that mass infantry offensives would never prevail over machine guns and artillery . General Pétain restored morale through a combination of rest rotations for front - line units , furloughs home , and stricter discipline . However , Smith has argued that the mutiniees were akin to labour strikes and can be considered political . The soldiers demanded not only peace , leave , and better food , and objected to the use of colonial workers on the home front ; they were also concerned about the welfare of their families . The courts - martial were merely symbolic , designed to demonstrate the absolute authority of the high command . The British government was alarmed , for it interpreted the mutinies as a sign of deep malaise in French society , tried to reinvigorate French morale by launching the Third Battle of Ypres , or Passchendaele . Kaiserschlacht . The French army was heavily involved in the defence of the allies ' line of defense during the final German offensives in spring 1918 . When the British troops were attacked during operation Michael , 40 French divisions were sent to help them . Those troops finally took part in the battle . Then , the third German offensive was launched against French positions in Champagne . The French troops began to lose ground but eventually , the Germans were stopped by a counterattack led by General Charles Mangin . In July , a last German assault was launched against the French on the Marne . The German troops were crushed by about 40 French divisions helped by British and American troops . This was a turning point in the war on the western front . The Grand offensive . During the summer of 1918 , General Ferdinand Foch was appointed supreme commander of the allied forces . After the decisive defeat of the Germans at the second Battle of the Marne , Foch ordered an offensive against Amiens . Some French units participated in this battle . Then , a general offensive was launched against the German positions in France . The French First Army helped the British troops in the north , while eight French field armies formed the center of the offensive . An additional army was sent to help the Americans . The French forces were the most numerous of all the allied troops , and during the last stage of the war , they took about 140 , 000 prisoners . The French forces remained the backbone of the allied offensive while the British Empire troops , helped by the French army , spearheaded it by attacking in Flanders and Western Belgium where they first smashed the Hindenburg line . Meanwhile , the French army managed to liberate most of northern France and to enter Belgian territory . These numerous offensives left the German army on the verge of disaster and when Germany sought for an armistice , the French and American troops were ready to launch an important offensive in Lorraine , where the Germans were collapsing . Other campaigns . While the French Army ' s main commitment was inevitably to the Western Front , significant forces were deployed in other theatres of war . These included the occupation of the German colonies of Togo and Kamerun in West Africa , participation in the Dardanelles and Palestinian campaigns against the Ottoman Empire and a diversionary offensive in the Balkans carried out in conjunction with other Allied forces . The bulk of the French troops utilized in these campaigns were North African and colonial units , both European and indigenous . However the substantial French reinforcements sent to the Italian Front in 1917 following the Battle of Caporetto were drawn from metropolitan French units , marking a diversion of resources from the Western Front . Equipment . At the outset of the war , the primary French field gun was the French 75 , ( 75mm caliber , entered service in 1897 ) . The French had about 4 , 000 of these guns , an adequate number , but despite accuracy , quick firing , and lethality against infantry , German howitzer s outranged the French 75 , which had a range of , by , and used heavier shells , inflicting more damage than the French guns . In 1913 , General Joseph Joffre authorized the limited adoption of the Canon de 155 C modèle 1917 Schneider , a howitzer with a range of over . When war broke out in August 1914 , the German Army had about 12 , 000 Maschinengewehr 08 machine gun s , the British and French armies had a few hundred . French models of machine gun used during the war included the Hotchkiss M1914 , the Chauchat , and the St . Étienne Mle 1907 . The first tank was ready for combat by January 1916 . Unaware of the British tank development programme , Colonel Jean Baptiste Eugène Estienne persuaded Joffre to begin production of French tanks . An order for 400 Schneider CA1 s and 400 St Chamond s was soon placed . The French deployed 128 tanks in April 1917 as part of the Second Battle of the Aisne , but they were unreliable . However , the Renault FT proved more worthy , and the French produced a total of 3 , 870 tanks by the end of the war . Grenade s came to the attention of German military planners as a result of the Russo - Japanese war of 1904 – 1905 , and by the beginning of the Great War , the Germans had 106 , 000 rifle grenade s and 70 , 000 hand grenade s . The French and Russian armies were better prepared than the British , expecting to find themselves besieging German fortresses , a task suited to the grenade . The French , along with the British , persisted in the use of rifle grenades , ( they used a special cup for launching ) , throughout the war , increasing their range from to . The mortar also interested the Germans , for a specific use : an invasion of France ' s eastern front . The advantage of a mortar was that it could be fired from the relative safety of a trench , unlike artillery . At the beginning of World War I , the German Army had a stockpile of 150 mortars , which was a surprise to the French and British . The French were able to use the century - old Coehorn mortars from the Napoleonic Wars . Subsequently , the French borrowed the design of the British Stokes Mortar , and collaborated on mortar designs with the British throughout the war . Eventually , large mortars could throw bombs . Despite the technological advances in grenades , machine guns , and mortars , the rifle remained the primary infantry weapon , in large part because other weapons were too cumbersome and unwieldy for an infantryman , and remained the weapon of choice for sniper s . Rifles remained virtually the same during the war years , mostly because research tended to be focused on larger weapons and poison gas . The average range of a rifle throughout World War I was , but most were only accurate to . The French rifle of choice was the Lebel Model 1886 , officially styled the Fusil Modèle 1886 - M93 , from 1886 , its major design flaw was its eight round tubular magazine which could cause explosions when the nose of one cartridge was forced onto the base of another . In 1916 , the Berthier rifle , officially titled the Fusil d ' Infanterie Modele 1907 , Transforme 1915 , was issued as an improvement , it was clip - loaded . The original , produced in 1907 , only held 3 rounds , but later versions in 1915 and 1916 held 5 and 6 rounds , respectively , and a carbine version of the Bertheir , dubbed the Berthier carbine , but titled Mousqueton modele 1916 , was released in 1916 . The carbine was preferred over a ' normal ' rifle because of the advantages in handling in a confined space , such as a trench , and was one of the few significant advances in rifle technology , although periscope s and tripod s were produced for trench warfare . Contrary to popular belief , the first country to use chemical warfare in World War I was not Germany , but France , who used tear gas grenades against the German army in August 1914 , however , the Germans were the first to seriously research chemical warfare . Poison gas , ( chlorine ) , was first used on April 22 , 1915 , at the Second Battle of Ypres , by the German army . April 1915 saw the first innovation in protection against chemical warfare : a cotton pad dipped in bicarbonate of soda , but by 1918 , troops on both sides had charcoal respirator s . By November 11 , 1918 , France had suffered 190 , 000 chemical warfare casualties , including 8 , 000 dead . Uniforms . At the outbreak of war the French Army retained the colourful traditional uniforms of the nineteenth century for active service wear . These included conspicuous features such as blue coats and red trousers for the infantry and cavalry . The French cuirassiers wore plumed helmets and breastplates almost unchanged from the Napoleonic period . From 1903 on several attempts had been made to introduce a more practical field dress but these had been opposed by conservative opinion both within the army and amongst the public at large . The adoption of a blue - grey ( " horizon - blue " ) uniform had been approved by the French Government in June 1914 but new issues had not been possible before the outbreak of war a few weeks later . The very heavy French losses during the Battle of the Frontiers can be attributed in part to the high visibility of the French uniforms , combined with peacetime training which placed emphasis on attacking in massed formations . The shortcomings of the uniforms were quickly realized and during the first quarter of 1915 general distribution of horizon - blue clothing in simplified patterns had been undertaken . The long established infantry practice of wearing greatcoats for field service , buttoned back when on the march , was continued in the trenches . The French Army was the first to introduce steel helmets for protection against shrapnel , and by December 1915 more than three million " Adrian " helmets had been manufactured . The horizon - blue uniform and Adrian helmet proved sufficiently practical to be retained unchanged for the remainder of the war , although khaki of a shade described as " mustard " was introduced after December 1914 for the North African and colonial troops serving in France .