At the outset of World War I, German forces attempted a rapid strike against France that, per the Schlieffen Plan, was intended to crush French resolve and free the entire German army for the Russian front within six weeks. This plan failed with the German reversal on the Marne, and both sides, unable to make headway against each other, settled in for a static war of attrition.
Mobile warfare had become nearly impossible in 1914 due to major technological advances in defensive weaponry. Machine guns and long-range rifles made cavalry charges and bayonet-equipped infantry nearly obsolete. Heavy artillery disrupted troop concentrations on both sides long before sufficient forces could be brought to the battlefield, and the trenches both sides dug were protected by barbed wire and land mines, which made any overland advance suicidal. In time, the trench network stretched from the Swiss border to the French coast, preventing any efforts to turn the enemy's flank. Under these conditions, most attempts at maneuver and assault failed to make significant progress. Aerial bombardment, mechanized armor and poison gas were all deployed in efforts to break the stalemate, but neither of the two sides proved able to permanently occupy the small amounts of territory they occasionally took.