The War’s First Major Battle on the Western Front Was its Most Important One
Germany almost won WWI in the first month of hostilities. The only reason it did not was because Germany’s chief of the general staff, Moltke the Younger, panicked in the first two weeks of fighting, and needlessly withdrew troops from the Western Front to reinforce the Eastern Front. If not for that, WWI would likely have been decided in Germany’s favor.
Germany planned to knock out France before her ally, Russia, fully mobilized. To that end, the Germans relied on the Schlieffen Plan, which envisioned a wheeling advance through Belgium and northern France in the shape of a sickle. The sickle’s tip would advance to the west of Paris, then swing back inwards and eastwards to bag the French armies in a giant sack.
However, Russia mobilized sooner than expected, and struck into Eastern Prussia. Moltke panicked, and despite advice by the Eastern Front’s commander that reinforcements were unnecessary, he transferred two corps from the Western Front to Eastern Prussia. They came from the right wing of the German wheeling advance into France. Before they arrived, the Battle of Tannenberg, the decisive battle of the Eastern Prussia campaign, had already been won by the Germans.
On the Western Front, withdrawal of the two corps weakened the German right wing, and a gap opened between the two rightmost German armies – a gap where the two corps sent to Eastern Prussia had been. Entente armies struck into the gap, and to close it, the German rightmost army was forced to wheel in early, east of Paris, instead of to its west as per the Schlieffen Plan.
Turning east of Paris exposed the German right flank to attack from troops in that city. That brought about the war’s most decisive battle, the First Battle of the Marne, when Entente armies attacked the Germans across the Marne River. The two rightmost German armies were threatened with encirclement and destruction, and Moltke had a nervous breakdown upon hearing the news.
His subordinates ordered a retreat, shattering German hopes of an early victory. Instead, Germany would end up fighting a war of attrition, in which the Entente would steadily bring their superior resources to bear, and steadily stack the deck against Germany. The Germans would never come as close to victory as they had during that first month of fighting.