About September 3 the enemy appears to have changed his plans and to have determined to stop his advance south direct upon Paris, for on September 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 September 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. [Sidenote: German columns converging on Montmirail.] 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 September 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. [Sidenote: Position of allies and Germans on September 6.] On the evening of September 6, therefore, the fronts and positions of the Allied Army were roughly as follows: _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. The position of the German Army was as follows: _Fourth Reserve and Second Corps._--East of the Ourcq and facing that river. _Ninth Cavalry Division._--West of Crecy. _Second Cavalry Division._--North of Coulommiers. _Fourth Corps._--Rebais. _Third and Seventh Corps._--Southwest of Montmirail. [Sidenote: First and Second German army.] All these troops constituted the First German Army, which was directed against the French Sixth Army on the Ourcq, and the British forces, and the left of the Fifth French Army south of the Marne. The Second German Army (IX., X., X.R., and Guard) was moving against the centre and right of the Fifth French Army and the Ninth French Army.