Final answer:
The Schlieffen Plan was a German World War I military strategy for a swift defeat of France through Belgium, after which forces would turn to face slower mobilizing Russia; however, it failed due to unexpected Belgian resistance and rapid Russian mobilization.
Step-by-step explanation:
The name of the German plan during World War I that aimed to avoid a two-front war by defeating France quickly and then turning east to fight Russia was the Schlieffen Plan. This strategy was based on the belief that Russia would be slow to mobilize, allowing Germany to swiftly attack and defeat France through Belgium. Field Marshal Alfred von Schlieffen, who anticipated that Germany would face enemies on both its eastern and western fronts, designed this plan.
The key concept was rapid mobilization and a swift attack on France to force a quick surrender. This would enable Germany to then focus its military might on Russia. The implementation of this plan at the outbreak of the war saw German forces invade Belgium on August 3, 1914, proceeding into Northern France according to the plan's outline. However, the plan ultimately failed due to unanticipated resistance from Belgium and quicker-than-expected Russian mobilization, which drew German forces away from the Western Front. Despite initial successes, the Schlieffen Plan did not result in the swift victory Germany had hoped for, leading to the drawn-out trench warfare that characterized much of WWI.