End of the Battle of Montdidier

On 15 August 1918 the Battle of Montdidier ended, the French part of the Allied attack begun a week earlier at Amiens. That day Marshal Ferdinand Foch agreed with Field Marshal Douglas Haig that a further frontal attack on Roye would cost too much, and the commander of the French First Army, General Marie-Eugène Debeney, called off the blow planned for 16 August. His army passed from Haig’s orders back under French command.

In practice the attack had already stalled several days earlier. After retaking Montdidier on 10 August the French, like the British, came up against a belt of old trenches and wire from 1915–1916, where the Germans had organised a new defence. On 11 August XXXI Corps of the First Army gained barely a kilometre and was still 3–4 km from Roye. General Georges Humbert’s Third Army, attacking on Debeney’s right towards Lassigny, pushed the German rearguards back another 1–4 km, but on 12 and 13 August achieved little more. On the same day that the British broke off the Battle of Amiens, Debeney postponed further attacks, because the army group commander, General Émile Fayolle, ordered him to withdraw some of his divisions into reserve: his army’s front had shortened by a third.

On 12 August Foch demanded a strong, concentrated blow by the First Army and the right wing of the British Fourth Army on the road junction at Roye, supported by the Third Army and, further east, by General Charles Mangin’s Tenth Army. The attack was fixed for 15 and then for 16 August. On the afternoon of 14 August Foch, on his way to Philippe Pétain, was overtaken by a British officer who had flown in with a letter from Haig. Haig wrote that German artillery fire on the Chaulnes–Roye line had markedly increased and the positions were strongly held, and he postponed the attack until it had been properly prepared. Foch replied that delay would have “the gravest consequences”. On the morning of 15 August at Sarcus, however, Debeney admitted to him that the attack on Roye would be difficult and that his forces, even if sufficient for the blow, would be too weak to follow it up. In the afternoon Haig repeated his arguments and proposed instead an attack by the British Third Army north of the Ancre, which would outflank the German line on the Somme. Foch let himself be persuaded and changed his orders. In the afternoon Debeney informed his corps commanders that the attack of 16 August was cancelled and that the artillery was to carry out only methodical destruction of targets, saving ammunition. That day the First Army was returned to the orders of Fayolle and Pétain.

According to figures that the British official history quotes from French sources, the First and Third Armies took about 11,400 prisoners and 259 guns between 6 and 15 August, losing 24,232 men. They recovered Montdidier and pushed the Germans back from the Paris–Amiens railway, but took neither Roye nor the hills of the Lassigny massif. This front did not stand still for long, however. Foch declared that the results of the victory must be extended by widening the battle on the flanks: on 17 August the French attack known as the Second Battle of Noyon began between the Oise and the Aisne, and a few days later the British Third Army struck near Albert.