"Following the victories in Belgium, von Moltke was convinced he would be able to implement the Schlieffen plan, and that Paris was now within the reach of his troops. The French army had reached the Marne and was waiting for the battle that was to decide the fate not only of France, but of the entire war."
The British resistance in Mons had allowed the French armies to retreat in good order towards Paris, stopping on the left bank of the Marne. The commander-in-chief of the French troops, General Joffre, was determined to hold the capital at all costs, by placing all the armies available to him at its defence. German troops had advanced for over 300 kilometres and were now ready to launch the final attack on Paris with a "hammer blow" from the west, where the 1st army of von Kluck was advancing.
Despite their apparent invincibility, the German forces were exhausted from the marches and fighting and were short on supplies due to the longer logistic chain. Added to these problems were von Moltke’s difficulties in communicating with his armies and heavy pressure from Berlin to obtain a swift victory. The effective Anglo-French defence also complicated matters. In the face of the tough resistance offered by the Vth French army at Guise and the BEF at Le Cateau, the Ist German army was forced to divert its advance. At the same time, the IInd army of von Bülow, engaged in fierce battles on the Marne, requested the intervention of Kluck’s troops to the east of Paris to weaken the French resistance and open the road toward the capital. The difficulties encountered by the Germans on the other side of the front had allowed the remaining forces of the Vth army and the BEF to retreat to the French capital. Joffre, however, predicted Kluck’s sudden deviation to the southeast and planned a counter-offensive. The French counterattack should have started on September 6th by engaging the Ist German army, which had left its right flank unprotected to attack the BEF; it would then place itself between the VIth and Vth French army. However, on September 5th, General Gallieni anticipated Joffre by moving the VIth army against Kluck’s troops. The battle of the Marne had begun.
Joffre supported Gallieni by sending all available units to the front. To speed up the flow of reinforcements, 600 taxis were requisitioned, transporting six thousand soldiers in just two trips. Although the furious French attacks blocked the German advance, they failed in their intention to undermine the front. On September 7th, Joffre ordered a mass attack by the Vth army and the BEF. The allies thus succeeded in wedging themselves between the Ist army of Kluck and the IInd of Bülow. Both Generals were short of men and supplies due to the fierce attacks of the VIth and IXth French army. On September 9th, the Allied troops managed to overcome the Marne and attempted to split the German front in two. The latter, however, gave no signs of yielding. At this point, Moltke, it is not known whether through excess caution or as the result of a “panic attack,” ordered his men to suspend the attacks and to retire to defensible positions. This torpedoed the Schlieffen plan along with the possibility of a quick victory.
In addition to Joffre’s insight and the bravery of the allied soldiers, the failure of the plan may be ascribed to a series of events. First of all, the front of the German attack was weakened as the German armies were spread along too wide a line. Schlieffen had established that, in the event of an attack on France, 90% of the forces were to converge on the right wing, while the remainder would take a stand in the Rhine valley and to the east to respond to any French and Russian attack. However, Moltke, not as daring as Schlieffen, placed only 60% of the troops on the right wing and dispersed the remainder in other areas. Obsessed by a French advance in Alsace-Lorraine, von Moltke strengthened the right wing with enormous numbers, insufficient, however, to weaken France. The left wing, which only had to act as bait, provided excessive forces for defence, but insufficient for counterattacks. Despite its limitations, Plan XVII indirectly helped disperse the Kaiser’s troops through its persistent offensive towards the German border, putting a wedge in Schlieffen’s "revolving door."
The second element against the Germans came from the east. Russia succeeded in mobilising its troops more quickly than first expected and invaded East Prussia, forcing Moltke to defend this area with more numerous forces. Although the Hindenburg armies were finally able to crush the Tsarist troops at Tannenberg and Masuria, the Russian offensive diverted many German divisions from the western front, thus relieving the pressure on the French.
With the operations of September '14 on the western front, all hope faded that the war would be concluded quickly. The battle of Marne alone claimed half a million dead, wounded, or missing among the French, English, and Germans. A brief, final stage began in 1914 that would be called the "Race to the sea." Trench warfare was looming.