Thirty miles northeast of Paris, the French 6th Army under General Michel-Joseph Maunoury begins attacking the right flank of German forces advancing on the French capital. By the next day, the counterattack was total. More than two million soldiers fought in the Battle of the Marne, and 100,000 of them were killed or wounded. On September 9, the exhausted Germans began a fighting retreat to the Aisne River. The Battle of the Marne was the first significant Allied victory of World War I, saving Paris and thwarting Germany's plan for a quick victory over France.
After the outbreak of hostilities in Europe in August 1914, Germany took the offensive in the West, hoping to defeat France before the Russians were able to fully mobilize in the East. The Germans rushed across Belgium, routing the Allies, and by September the "Schlieffen Plan"--the planned outflanking of the French forces--seemed headed to a triumphant conclusion. In early September, German forces crossed the Marne River to the northeast of Paris, and the French government was evacuated to Bordeaux.
As retreating French forces and the British Expeditionary Force scrambled to prepare a counterattack, they were dealt a lucky hand when precise information about the German plan of attack was found in a knapsack retrieved from a slain German officer. The French had thought that German General Alexander von Kluck's 1st Army would march into the Oise Valley, but the plan told of a direct march on Paris. The French commander in chief, General Joseph Joffre, coordinated the information into his battle plans, and on the afternoon of September 5 the French 6th Army under General Michel-Joseph Maunoury surprised the right flank of Kluck's 1st Army near the Marne River.
Kluck turned his army to meet the French 6th Army, creating a gap between his 1st Army and German General Karl von Bulow's 2nd Army, 30 miles to the southeast. The French 5th Army then turned and rushed into the gap to attack BÝlow, and the British Expeditionary Force halted its retreat and turned to likewise advance into the gap. Meanwhile, to the west of the German 2nd Army, the newly created French 9th Army attacked the German 3rd Army.
For three bloody days, the battle shifted back and forth along a 100-mile front. The French 6th Army stubbornly held its ground under heavy counterattacks by Kluck's 1st Army, and at one point 600 Paris taxicabs were enlisted to drive 6,000 French troops from the capital to the battle front. The fighting was so near the city that the automobiles could make the trip there and back on a single tank of gas.
On September 9, General Bulow learned of the approach of the British Expeditionary Force and ordered his 2nd Army to retreat. General Kluck and the German 1st Army had no choice but to follow, and by September 11 the retreat extended to all the German armies. The Germans retreated 40 miles north to the Lower Aisne River, where they dug trenches and succeeded in repelling successive attacks by the pursuing Allied forces. Both sides then tried and failed to outflank each other in the "Race to the Sea," in which trench networks were extended northwestward by both sides until they reached the Atlantic at a point inside Belgium.
Because it defeated Germany's Schlieffen Plan and also ended Allied hopes for a quick end to the war, the First Battle of the Marne ranks as one of the most decisive battles in history. Around 100,000 soldiers were killed or wounded in its six days of heavy fighting, roughly an equal number on each side. By the end of 1914, well over a million soldiers of various nationalities had been killed on the battlefields of Europe, and neither for the Allies nor the Central Powers was victory in sight. On the western front--the battle line that stretched across northern France and Belgium--the combatants settled down in the trenches for a terrible four-year war of attrition.