Warmatrix

The First Battle of the Marne in 1914 CE was one of the most important battles of World War I. It stopped the German advance and was the starting point for four years of trench warfare.
At the start of the war, the German army swept into northern France through Belgium, following the Schlieffen plan. This envisioned a sickle-like maneuver with the aim of ultimately capturing Paris. Initially the plan went well; in several battles spread over 2½ weeks the Belgian army and British Expeditionary Force were driven back to the west and the French one also forced into a great retreat, to as little as 50 kilometers from Paris. Von Schlieffen had not found a theoretical solution to deal with the problems of slow advance on foot and the obstacle that Paris formed. Now, in practice, the German generals did not know how to deal with the situation either. They followed the course of events and decided to pass the city on the left. It was a mistake; instead of attempting to encircle a substantial part of the allied forces, they were now themselves in danger of being encircled.
Meanwhile the French general Jouffre reorganized his battered forces around the river Marne, which was a natural frontline between Paris and Verdun. He assembled 39 French and 6 British divisions, to be pitted against 27 German ones. Two weeks after the start of the retreat he was able to launch a counteroffensive, which became the First Battle of the Marne.
The battle opened in the west, where the Germans quickly reacted to the allied advance, strengthened their right flank and stalled the attack. However this created a gap between the first two German armies that were engaged. The allies sent their soldiers into the gap, which threatened to tear the German frontline apart. The Germans launched several counterattacks, but the French and British troops, reinforced just in time, held firm. In early September the German commanders realized the danger and decided to retreat some 60 kilometers to well-defensible positions around the river Aisne. Trenches were dug; barbed wire laid; machine guns installed: the trench war began.
More than 2 million men fought in the battle. Casualties are roughly estimated at half a million, equally divided between Germans and allies. The allied victory saved Paris and kept France in the war, but did not knock out the German army. After the battle both sides tried to extend their front to the northwest in what is called the Race to the Sea. This established a long frontline that stretched from the sea to Switzerland.