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First Battle of the Marne
September 5–12, 1914· Battle· Europe
Well documentedSolid records, physical evidence or scientific consensus.
French and British forces halted the German advance on Paris and forced a retreat, ending hopes of a quick war in the West.
See it on the Battles & Wars map →What happened
In August 1914 German armies swept through Belgium toward Paris, aiming to knock France out within weeks. Exhausted and stretched, General von Kluck's First Army swung east of Paris, exposing its flank. French commander Joseph Joffre counterattacked with the British Expeditionary Force and a new army from Paris, some rushed forward in requisitioned taxis. A gap opened between two German armies, and from September 9 they retreated about 40 miles to the Aisne River. About 2 million men fought; casualties neared 500,000, by varying estimates.
Why it matters
It wrecked Germany's plan for a quick victory in the West, condemning it to a long two-front war and leading to four years of trench deadlock.
How we know
French and German official histories, army orders, commanders' memoirs, and a German inquiry into staff officer Richard Hentsch, who approved the retreat.
Still debated
Whether the German retreat was necessary, and how much blame belongs to Moltke the Younger or Hentsch, is still argued; the taxis' role is often exaggerated.
Connections (3)
▸First Battle of the Marne led to Trench warfareWell documented
The connection
Retreating from the Marne, the Germans halted on high ground above the Aisne River and dug in. French and British attacks on those trenches in mid-September failed against machine guns and artillery. Each side then tried to turn the other's open northern flank, and each attempt ended with both digging in, stretching the trench line toward the sea.
When and how
First Battle of the Aisne, September 13–28, 1914, then the Race to the Sea through Picardy, Artois and Flanders to the Belgian coast by October.
How we know
Army war diaries and orders from mid-September 1914 show units told to entrench; historians widely date the trench era to the Aisne.
Debates and open questions
Some historians argue trenches were inevitable given 1914 firepower, and that the Marne only decided where, not whether, the front would freeze.
▸First Battle of the Marne ended hopes for a quick World War IWell documented
The connection
Germany's war plan depended on beating France in about six weeks, then turning on Russia. The Marne ended that hope. Moltke the Younger, Germany's chief of staff, broke down under the strain and was replaced by Erich von Falkenhayn. Germany now faced the long two-front war its planners had feared, against enemies with more people and resources.
When and how
The Marne valley east of Paris, September 1914; Moltke was relieved on September 14; French commander Joseph Joffre was hailed as 'the victor of the Marne'.
How we know
German leaders' letters and memoirs show they knew the plan had failed; Moltke reportedly told the Kaiser the war was lost, though the quote is uncertain.
Debates and open questions
Whether Germany could have won quickly at all is debated; Russia's faster-than-expected invasion of East Prussia led Moltke to send two corps east.
▸Military railways rushed French reserves in time for the First Battle of the MarneWell documented
The connection
As the Germans swept through Belgium toward Paris, they outran their own railheads; wrecked lines left their troops marching far from supplies. France, using intact railways behind its lines, shifted divisions from Lorraine to form new armies near Paris. These struck the exposed German flank in September 1914.
When and how
Northern France, late August–September 1914; Joffre's French high command moved troops to Maunoury's Sixth Army and Foch's Ninth Army.
How we know
French railway and staff records document the troop movements; German supply problems are recorded in their own war diaries.
Debates and open questions
The famous Paris taxis carried only a few thousand men; how much rail logistics, versus German command errors, decided the battle is debated.