5 - 9 September 1914
The Battle of the Marne begins in the early afternoon of 5 September, when elements of the French Sixth Army, defending Paris, attack the right flank of Kluck's German First Army, in the vicinity of Meaux. Believing that the BEF has been destroyed in its rearguard action at Le Cateau (25/6 August), and that the French Fifth Army ahead of him is still in retreat, Kluck wheels his army westward to confront the French Sixth Army with a fierce counter-attack on 6/7 September. He succeeds in halting the advance of the French Sixth Army, but by moving west creates a gap of about 30 miles between himself and von Bulow's Second Army, which the Germans have no reserves to fill.
Into this gap march the BEF and elements of the French Fifth Army, which advance north and recross the Marne on 9 September. This manoeuvre separates the German First and Second Armies, exposing both to attack in the flank and rear, and forcing both to retreat. By the afternoon of 9 September, the First and Second Armies have begun their withdrawal north, and within 4 days they have retreated 60 miles to the River Aisne. The threat to Paris has been lifted, though at the cost of over 80,000 casualties on the Allied side. (German casualty figures are never published).
