Excerpts from Books and Wikipedia
"The Battle of the Marne (French: Première bataille de la Marne, also known as the Miracle of the Marne, Le Miracle de la Marne) was a World War I battle fought from 6–10 September 1914. It resulted in an Allied victory against the German armies in the west. The battle was the culmination of the German advance into France and pursuit of the Allied armies which followed the Battle of the Frontiers in August and had reached the eastern outskirts of Paris. A counter-attack by six French armies and the British Expeditionary Force (BEF) along the Marne River forced the Imperial German Army to retreat north-west, leading to the First Battle of the Aisne and the Race to the Sea. The battle was a victory for the Allies but led to four years of trench warfare stalemate on the Western Front. . . . The significance of the battle centres on its undermining of the Schlieffen Plan, which forced Germany to fight a two-front war against France and Russia—the exact scenario that its strategists had long feared. Historian Richard Brooks claimed that, "By frustrating the Schlieffen Plan, Joffre had won the decisive battle of the war, and perhaps of the century." [Wikipedia]