By September I, 1914, it was plain to the Germans that the French army had escaped its embrace and that no envelopment was longer possible. It remained possible to destroy them by main force, since German numbers were still superior, German artillery unchallenged, and the early successes productive of unbounded confidence. The German armies thus leaped forward for the final decisive battle, which had been just missed at the French frontier. (Vol. II, 84, 85.)
But the new situation imposed new strategy. It was no longer possible to envelop the Allies, and accordingly, Kluck, on the western flank, turned southeast and marched across the face of Paris, crossing the Marne near Meaux and leaving only one corps to guard his flank toward Paris. This was a sound maneuver, if the French troops in Paris were too few or too broken to strike; it was perilous in the extreme, if the opposite were the case. And it was the case, for Joffre had concentrated behind Paris a new army, Manoury's, which was now to attack.
On September 5, 1914, the Germans having now fallen into Joffre's trap, the French commander in chief issued his famous order, and the whole Anglo-French army suddenly passed from the defensive to the offensive. (Vol. II, 102.) The first shots of the conflict, the great Battle of the Marne, were fired by some German field pieces, at Monthyon, just north of the Marne and less than twenty miles from Paris. They greeted the advance of Manoury's army coming east out of Paris and striking at Kluck's open flank. (Vol. II, 103.)
September 6, 1914, the Battle of the Marne.
The next day Manoury rolled up Kluck's flank, drove his troops in on the Ourcq River, and threatened his army with destruction. Kluck saved himself by extraordinary clever work, he drew his troops back from the front of the British south of the Marne, put them in against Manoury and by September 10, 1914, had driven Manoury back toward Paris and was threatening him. The first blow had failed, but it had brought a chain of consequences fatal to German plans. (Vol. II, 99-110.)
First of all the British, once Kluck had drawn his main masses from their front, began somewhat tardily to advance, threatening Kluck's other flank, and Franchet d'Espérey's army, to the east, about Montmirail, in turn, attacked Bülow's, whose position had been made dangerous by the retreat of Kluck. Bülow had to go back north of the Marne, suffering severe losses and his retirement uncovered the flank of Hausen's army fighting to the east from La Fère Champenoise to Vitry. (Vol. II, 107.)
Meantime things had been going badly on this line for the French, and their troops under Foch had been driven back many miles. The Germans, feeling the danger from the west, were making one final effort to break the French center and win the decisive contest. But Bülow's retreat opened the way for a supreme piece of strategy on the part of Foch, who descended from the heights, struck Hausen, almost routed him and sent him in quick retreat beyond the Marne. (Vol. II, 120, 121.)
This settled the battle. Kluck, Bülow, and Hausen were now forced to retreat, their retreat communicated itself all along the line and by September 13, 1914, the Germans were all withdrawing, Kluck was over seventy miles north of the Grand Morin, just taking root behind the Aisne, the Battle of the Marne was over, and the great German plan to deal with France in six weeks had been completely wrecked. Actually the first phase of the war was over, unless the Germans could regain the offensive and restore the conditions existing before the Marne. (Vol. II, 120-123.)