Germany's plan to knock France out of the war with an early strike had clearly failed by early September 1914. The Allies had halted the German drive toward Paris during the First Battle of the Marne, resulting in a stalemate. The series of battles and engagements that followed would later become known as the Race to the Sea, in which the Germans and Allies took turns attempting to flank each other to the north until they reached the North Sea. With operational-level flanking maneuvers impossible, both sides dug in, creating a long line of opposing trenches and defensive works that reached all the way to the Swiss border. As a result, any progress on the Western Front now required direct assaults on strongly held enemy lines. Given these conditions, the German General Staff reached the painful conclusion that a swift and decisive victory in the west was essentially impossible.