The Schlieffen Plan was part of Germany's plan for a two front war with France and Russia. France was to be knocked out of the war quickly by an attack through neutral Belgium. The main French armies were on the Franco-German border, where they would be allowed to advance into Germany, preventing them from interfering in the German attack, which would sweep to the west of Paris, cutting off the French capital.
The plan came close to success in 1914, but it had been diluted before the outbreak of war. The German armys on the French border had been strengthened, reducing the strength of the army involved in the attack through Belgium. The German plan had also failed to account for any British intervention, but the small but professional British army landed in the exact area that the Germans needed to attack through.
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