The Battle of the Marne: 8–9 September 1914

Between 8–9 September 1914 the German advance into France was halted by the Allies. That night the French 5th Army capitalized on the resolution shown by the 6th Army and counterattacked the German 2nd Army, cleaving a broader gap between the two German armies. The German Chief of Staff, Herman von Moltke, failed to give the German armies clear orders and his field commanders began ordering retreats. Fearing encirclement, the 2nd Army was the first to pull back, followed by the 1st Army. They were driven back 40 miles (64 km) before regrouping at the River Aisne. The remaining German armies to the east, despite being close to forcing a French retreat around Verdun, were also ordered to join the general withdrawal. The Marne is generally considered to be the death knell of the Schlieffen Plan, which was based on the assumption that Germany would defeat France in six weeks.