Final answer:
The Schlieffen Plan, developed by Germany to avoid a two-front war by quickly defeating France and then Russia, failed due to the underestimation of opposition forces and misjudging Russian mobilization, leading to prolonged trench warfare.
Step-by-step explanation:
The Schlieffen Plan was predicated upon the assumption that Germany would have to fight a two-front war against Russia and France. It required a rapid mobilization and defeat of France by moving through Belgium before turning to face the slower-to-mobilize Russian forces. However, the plan failed due to several reasons:
- Underestimation of Belgian and French resistance.
- Incorrect assumption that Britain would not defend France.
- Misjudgment of the Russian mobilization speed.
These miscalculations led to Germany fighting on multiple fronts, the very scenario the Schlieffen Plan was designed to avoid. The German troops were stretched thin, and the initial rapid advance into France eventually stalled, leading Germany into a prolonged conflict that descended into trench warfare.