Final answer:
The Battle of the Mons and the Battle at Le Cateau delayed the German advance, disrupting the Schlieffen Plan, which was intended to swiftly defeat France before turning to Russia, thus contributing to a prolonged two-front war.
Step-by-step explanation:
The Battle of the Mons and the Battle at Le Cateau were significant encounters during the first month of World War I. At the Battle of the Mons on August 23, 1914, British troops fought a strong defensive action against the advancing Germans, but they had to retreat due to the overpowering numbers of German troops aligned against them. The subsequent action at Le Cateau on August 26 provided a rear-guard action that further delayed German advances.
These battles helped cause the failure of the Schlieffen Plan, a German offensive aimed to quickly defeat France by attacking through Belgium and avoid a protracted war on two fronts. The plan, however, underestimated the resistance of Belgium and France, assumed that Britain wouldn't quickly come to France's aid, and incorrectly presumed that Russia would be slow to mobilize.
As a consequence, Germany encountered unexpectedly fierce resistance and was forced to engage in a war on two fronts, which the Schlieffen Plan had specifically aimed to avoid. Faced with the British Expeditionary Force in the west and the rapid mobilization of Russian troops in the east, Germany's initial offensive was stalled. This failure eventually led to the establishment of trench warfare, characterizing much of the Western Front and resulting in a drawn-out and costly conflict.