General Joffre announced to me his intention of wheeling up the left flank of the 6th Army, pivoting on the Marne and directing it to move on the Ourcq; cross and attack the flank of the 1st German Army, which was then moving in a south-easterly direction east of that river. He requested me to effect a change of front to my right—my left resting on the Marne and my right on the 5th Army—to fill the gap between that army and the 6th. I was then to advance against the enemy in my front and join in the general offensive movement. These combined movements practically commenced on Sunday, September 6th, 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 6th French Army, through Lizy on the Marne, Mauperthuis, which was about the British centre, Courtaçon, which was the left of the 5th French Army, to Esternay and Charleville, the left of the 9th Army under General Foch, and so along the front of the 9th, 4th, and 3rd French Armies to a point north of the fortress of Verdun. This battle, in so far as the 6th French Army, the British Army, the 5th French Army, and the 9th French Army were concerned, may be said to have concluded on the evening of September 10, by which time the Germans had been driven back to the line Soissons-Reims, with a loss of thousands of prisoners, many guns, and enormous masses of transport. About the 3rd September the enemy appears to have changed his plans and to have determined to stop his advance south direct upon Paris, for on the 4th September air reconnaissances showed that his main columns were moving in a south-easterly direction generally east of a line drawn through Nanteuil and Lizy on the Ourcq. On the 5th September several of these columns were observed to have crossed the Marne, whilst German troops, which were observed moving south-east 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 Ferté, Nogent, Château Thierry, and Mezy. Considerable German columns of all arms were seen to be converging on Montmirail, whilst before sunset large bivouacs of the enemy were located in the neighbourhood of Coulommiers, south of Rebais, La Ferté-Gaucher, and Dagny. I should conceive it to have been about noon on the 6th September, 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 6th French Army north of the Marne towards the Ourcq became apparent, that the enemy realised the powerful threat that was being made against the flank of his columns moving south-east, and began the great retreat which opened the battle above referred to.