Between 5 and 12 September 1914, French and British armies turned on the German right wing east of Paris and forced it back to the Aisne. Kluck's German First Army had wheeled south-east, passing east of the capital; when Maunoury's new Sixth Army struck its flank on the Ourcq, Kluck swung his corps back west to meet it and opened a gap of tens of kilometers between his army and Bülow's Second. The BEF and Franchet d'Espèrey's Fifth Army advanced into that gap while Foch's Ninth Army held at the marshes of Saint-Gond. On 9 September, after Lieutenant-Colonel Hentsch's mission from German headquarters, Bülow and then Kluck ordered a retreat. The battle ended German hopes of a quick victory in the west. This is an operational-scale map: blocks are corps and divisions on approximate fronts, not trench lines.
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This is an operational-scale map: each block is an army corps or a division, drawn as an approximate front several kilometers wide, as on the British official history and West Point atlas maps. After a month of advance through Belgium and northern France, the German right wing is closing on Paris: Alexander von Kluck's First Army on the outer flank, Karl von Bülow's Second Army to its left and Max von Hausen's Saxon Third Army beyond. At the end of August Kluck wheels south-east to stay on the heels of the retreating French Fifth Army, so that his army passes east of Paris instead of enveloping it; he crosses the Marne on 3 September, leaving only Hans von Gronau's IV Reserve Corps north of the river as a flank guard. British airmen report the wheel from 1 September. In Paris, General Joseph Gallieni, military governor, sees the German flank exposed, and on 4 September Joffre issues his Instruction No. 6 for a general offensive on the 6th. The new French Sixth Army under Michel-Joseph Maunoury assembles north-east of Paris; the British Expeditionary Force (BEF) and the Fifth Army, now under Louis Franchet d'Espèrey, are still retreating south of the Grand Morin.
Maunoury's army moves east toward the Ourcq a day early. Around midday its reserve divisions (Lamaze's 55th and 56th) and the Moroccan Brigade run into Gronau's IV Reserve Corps on the heights of Monthyon, Penchard and Saint-Soupplets, north-west of Meaux. Gronau, guessing that a large force is coming at Kluck's flank, attacks first. The French reservists advance across open beet fields near Iverny and Villeroy without artillery support and lose heavily; the poet Charles Péguy, a lieutenant in the 276th Infantry, is killed at Villeroy that afternoon. That night Gronau falls back about 10 km to a better line behind the Thérouanne brook, toward the Ourcq, and warns Kluck. South of the Marne, the German First Army's other corps are still pushing south-east against the French Fifth Army near Courgivaux and Esternay, while the BEF, by the British official history's reckoning, lies 10 to 20 miles behind where Joffre expected it.
On the 6th Joffre's offensive opens along the whole front from Paris to Verdun. On the Ourcq the Sixth Army closes up to the line Varreddes-Étrépilly-Acy and by the 7th reaches Penchard-Étrépilly-Betz, with the 45th (Algerian) Division and the 61st Reserve Division and Sordet's cavalry coming into line. To save his flank, Kluck pulls first his II Corps (6 September) and then his IV Corps (7 September) back north across the Marne to the Ourcq, and soon decides to bring his III and IX Corps as well. Each move strips the ground between the Marne and the Petit Morin, leaving a gap of some 30 to 50 km between the First and Second Armies (sources differ on its width) that is held only by the cavalry of Marwitz and Richthofen and a few rifle battalions. The French 8th Division, in the gap south of the Marne at Chessy, declines to attack, citing fatigue.
With Maunoury's left threatened, Gallieni throws in the newly arrived IV Corps. Most of its 7th Division comes by train, but on the night of 6 September about 630 Paris taxis gather at the Esplanade des Invalides, collect men of the 103rd and 104th Infantry at Gagny and Villemomble, four or five to a cab, and, after a day's wait, drive them out on the nights of 7-8 September toward Nanteuil-le-Haudouin and Silly-le-Long. By one count about 5,000 men arrive by the morning of the 8th, and most are kept in reserve. The Musée de l'Armée calls their military role 'very secondary', and historians treat the episode as more symbolic than decisive; the taxis became the emblem of Paris's resolve. Meanwhile Kluck's III and IX Corps march north across the Marne to extend his line on the Ourcq.
Into the empty space between Kluck and Bülow march the BEF and Franchet d'Espèrey's Fifth Army. The BEF turns north on 6 September and on the 7th crosses the Grand Morin around Coulommiers, Chauffry and Jouy-sur-Morin against German cavalry rearguards. On the 8th it forces the Petit Morin, a canal-like stream about 20 feet wide with few bridges, at Sablonnières, La Trétoire, Bellot, Orly and Saint-Cyr, and reaches Signy-Signets and the edge of La Ferté-sous-Jouarre; the official history notes that the advance was cautious. On its right the Fifth Army's XVIII Corps reaches L'Épine-aux-Bois and its III Corps comes within two miles of Montmirail; Bülow bends back his right wing (VII Corps) to face west. Allied airmen report the columns moving into the gap.
Further east, Ferdinand Foch's new Ninth Army has orders to hold the southern exits of the marshes of Saint-Gond, a wet valley crossed by only a few causeways, and cover the Fifth Army's right. Bülow's X Reserve and X Corps press from the north-west and the Prussian Guard and Hausen's Saxons from the north-east. Before dawn on 8 September the Guard and the Saxons make a bayonet attack without artillery preparation across the Somme-Soude near Normée and drive Foch's right (XI Corps) back past Fère-Champenoise. On the morning of the 9th German troops take the château at Mondement, the ridge village at the western end of the marshes; that evening the 77th Infantry and the Zouaves of Humbert's Moroccan Division retake it. Foch moves Grossetti's 42nd Division behind his line to his hard-pressed center. His famous message 'My center gives way, my right falls back; situation excellent, I attack' is probably apocryphal, but it captures how he fought.
In Luxembourg, Moltke has no clear picture and sends Lieutenant-Colonel Richard Hentsch of the General Staff on a tour of the armies with authority to coordinate a retreat if one proves necessary. On the evening of the 8th, at Second Army headquarters at Montmort, he finds Bülow convinced that his army is near collapse and that Allied columns in the gap will turn his right. On the morning of the 9th Bülow decides to retreat. Hentsch drives through the gap to First Army headquarters at Mareuil-sur-Ourcq, where, by most accounts, he meets Kluck's chief of staff, Hermann von Kuhl, and the First Army is ordered back as well, just as Quast's IX Corps is pressing the French left near Nanteuil-le-Haudouin. The same day the BEF crosses the Marne between La Ferté-sous-Jouarre and Château-Thierry, at Nogent, Charly, Nanteuil-sur-Marne and Saacy, against rearguards; Brigade Kraewel holds it near Montreuil-aux-Lions. Whether Hentsch exceeded his authority has been argued ever since.
The German First, Second and Third Armies fall back north, the First to the heights above the Aisne north of Soissons, the Second toward the Vesle and Reims; the Allied pursuit, slowed by rain, exhaustion and blown bridges, reaches the Aisne on 12-13 September (positions here are schematic). Paris is saved and the German plan for a quick decision in the west has failed; within days Moltke is replaced by Erich von Falkenhayn. Losses were enormous on both sides; one recent estimate puts Allied casualties at about 263,000, with German losses similar. The armies' attempts to turn each other's open flank to the north, the 'Race to the Sea', followed, and the front settled into trenches that would last four years.
Most of the Marne battlefield is still open farmland, woods and villages, and the Ourcq fields north-west of Meaux are described as almost unchanged; the big differences are at the western edge, where Paris has spread east along the Marne (the new town of Marne-la-Vallée) and Charles de Gaulle airport now covers the plateau north-east of the city, and at Saint-Gond, where the marshes have been partly drained, cultivated and planted with poplars.
The interactive map can show the period landscape (3 shapes: Paris-Charles de Gaulle airport (opened 1974), Marne-la-Vallée new town (from 1972), core built-up area, Marshes of Saint-Gond, approximate 1914 wet valley) under the units. Open the map.
At First Marne: Standard German infantry rifle.
The Mauser-designed Gewehr 98 was the standard German infantry rifle of World War I. Its controlled-feed bolt action proved so sound that it became the basis for countless military and sporting rifles worldwide, including the later Karabiner 98k.
At First Marne: German machine gun, issued to each regiment's machine-gun company.
Germany's licensed version of the Maxim gun, the water-cooled MG 08 was the backbone of German defensive firepower in World War I. Heavy but extremely reliable, it was usually fired from a sled mount by a trained crew and could sustain fire for long periods.
At First Marne: The German field gun of 1914.
The FK 96 n.A. ("new model") was the standard German light field gun at the start of World War I, a 1904 rebuild of an older design with a modern recoil system. Allied soldiers often called its fast, flat-trajectory shells "whizz-bangs."
At First Marne: Standard French infantry rifle.
The Lebel was the first military rifle designed for smokeless-powder ammunition, a breakthrough that made every black-powder rifle obsolete. Though dated by 1914, it remained the main rifle of the French infantry throughout World War I.
At First Marne: The French 75, the decisive field gun on the Ourcq and the Saint-Gond marshes.
The French 75 was the first field gun with an effective hydro-pneumatic recoil system, letting it stay on target and fire very rapidly. The AEF received about 2,000 of them, and they became the main light gun of American artillery in France.
At First Marne: French heavy machine gun.
The air-cooled, gas-operated Hotchkiss was France's standard heavy machine gun in World War I and was known for its ruggedness. The American Expeditionary Forces adopted it in large numbers while US production of its own machine guns caught up.
Free for everyone every year on its anniversary: September 5–12.
The British official history (Edmonds 1914 vol. I) for BEF and neighboring French positions, French memorial and museum sources, and named histories; the French official history and Reichsarchiv cited but not read online.
Towns and villages (Meaux, Monthyon, Nanteuil, Château-Thierry, Montmirail, Mondement) are fixed; army and corps fronts are approximate at this scale.
Corps-level moves follow Edmonds and standard accounts; German Second and Third Army and Ninth Army positions, and 10–12 September, are schematic.
Accounts agree on the turning points; the width of the gap and Hentsch's meetings differ and are attributed.
