On the morning of 5 September, as Maunoury’s Sixth Army probed forward to take up attacking positions for the following day, he was seized by disquiet at the reports sent back by his attached cavalry division. Its patrols found advancing French troops all across its front. As the IV Reserve Corps was aligned at right angles to and to the rear of von Kluck’s First Army, that meant that the enemy was manoeuvring to take First Army in flank and roll it up. His response was instantaneous and courageous. He decided to attack.
