These combined movements practically commenced on Sunday, Sept. 6, at sunrise; and on that day it may be said that a great battle opened on a front extending from Ermenonville, which was just in front of the left flank of the Sixth French Army, through Lizy on the Marne, Mauperthuis, which was about the British centre, Courtecon, which was on the left of the Fifth French Army, to Esternay and Charleville, the left of the Ninth Army under Gen. Foch, and so along the front of the Ninth, Fourth and Third French Armies to a point north of the fortress of Verdun.

[Illustration:  Map 5.—­Sept. 8.  Battle of the Marne.  The great advance to the Petit Morin and the Marne, where important captures were made by the British.]

This battle, in so far as the Sixth French Army, the British Army, the Fifth French Army, and the Ninth French Army were concerned, may be said to have concluded on the evening of Sept. 10, by which time the Germans had been driven back to the line Soissons-Rheims, with a loss of thousands of prisoners, many guns, and enormous masses of transport.

About Sept. 3 the enemy appears to have changed his plans and to have determined to stop his advance south direct upon Paris, for on Sept. 4 air reconnoissances showed that his main columns were moving in a southeasterly direction generally east of a line drawn through Nanteuil and Lizy on the Ourcq.

On Sept. 5 several of these columns were observed to have crossed the Marne, while German troops, which were observed moving southeast up the left flank of the Ourcq on the 4th, were now reported to be halted and facing that river.  Heads of the enemy’s columns were seen crossing at Changis, La Ferte, Nogent, Chateau Thierry, and Mezy.

Considerable German columns of all arms were seen to be converging on Montmirail, while before sunset large bivouacs of the enemy were located in the neighborhood of Coulommiers, south of Rebais, La Ferte-Gaucher, and Dagny.

I should conceive it to have been about noon on Sept. 6, after the British forces had changed their front to the right and occupied the line Jouy-Le Chatel-Faremoutiers-Villeneuve Le Comte, and the advance of the Sixth French Army north of the Marne toward the Ourcq became apparent, that the enemy realized the powerful threat that was being made against the flank of his columns moving southeast, and began the great retreat which opened the battle above referred to.

On the evening of Sept. 6, therefore, the fronts and positions of the opposing armies were roughly as follows: 

    Allies.

    Sixth French Army.—­Right on the Marne at Meux, left toward Betz.

    British Forces.—­On the line Dagny-Coulommiers-Maison.

    Fifth French Army.—­At Courtagon, right on Esternay.

    Conneau’s Cavalry Corps.—­Between the right of the British and the
    left of the French Fifth Army.