The Battle of the Marne by G.H. Perris — Read

For it was no exaggeration to say that a rapid victory was an _essential_ condition of the German plan. The envelopment of the west wing of the Allies might succeed if it were effected by the time they reached the Somme, or a little beyond, but not later, and that for three main reasons. In the first place, there was, south of the Somme, Maunoury's force, not large at first, but constantly growing, a grave threat to Kluck's west flank, whether realised or not. In the second place, there was Foch's new army forming at the centre; and, between Lanrezac and Foch, Bülow's advance was so compromised that it had become necessary for Kluck to move eastward in order to relieve his comrade. Thirdly, Paris stood across the path of a more directly southward movement, with the certainty of delaying, and the probability of dislocating, an immediate attack. The design of envelopment by the west was, therefore, necessarily abandoned.

Between August 29 and September 1, when he had passed the Somme, Kluck ceased his south-westerly course, which no longer had any important purpose, and came in touch with Bülow, to support his blow at the strongest of the French Armies, the 5th. It was probably thought, on the following days, that Maunoury would be locked up in Paris by a distraught Government, and that the British Army, virtually disabled, would not require very serious attention. Personal ambition, fear of being late for the action that was to give a dramatic victory, may have spurred on the commander of the I Army. [48]