The Battle of the Frontiers was a series of battles fought along the eastern frontier of France and in southern Belgium shortly after the outbreak of World War I. The battles represented a collision between the military strategies of the French Plan XVII and the German Schlieffen Plan. The German idea, to concentrate their forces on their right flank and wheel through Belgium to attack the French in the rear, was foiled by the movement of General Charles Lanrezac's Fifth Army towards the northwest to intercept them and the presence of the British Expeditionary Force (BEF) on his left flank. Although driven back by the weight of three German armies, the French and British rear guard actions delayed the German advance, allowing the French time to transfer their forces to the west to defend P