The French may have conducted a successful defence on the Marne, but the Germans were not beaten. Although Foch had tried to make Ninth Army pursue the retreating enemy forces with all speed, little progress had been made and once the Germans reached the high ground north of the river Aisne progress ended. Moltke intended the retreat to be merely a temporary measure, and so the Germans dug defensive positions as soon as they reached the tactically favourable high ground. There Moltke filled the gap between First and Second Armies, and turned his attention to Belgium. Then War Minister Erich von Falkenhayn replaced Moltke as chief of the general staff on 14 September and set about re-starting the offensive so as to defeat the French as speedily as possible.

With the end of active operations on his front Foch turned to thinking about infantry tactics. The doctrine had been formation in depth [‘l’ordre en profondeur’], but this meant that when the heads of columns reached an obstacle such as a heavily defended trench and were held up, then all the rearward elements (reinforcements, second line and so on) stopped as well. As a tactic it was useless for getting troops forward without significant losses, and putting more troops into the first line only increased the casualties.