On August 8, 1918, the Allies launch a series of offensive operations against German positions on the Western Front during World War I with a punishing attack at Amiens, on the Somme River in northwestern France.

After heavy casualties incurred during their ambitious spring 1918 offensive, the bulk of the German army was exhausted, and its morale was rapidly disintegrating amid a lack of supplies and the spreading influenza epidemic. Some of its commanders believed that the tide was turning irrevocably in favor of Germany’s enemies; as one of them, Crown Prince Rupprecht, wrote on July 20, “We stand at the turning point of the war: what I expected first for the autumn, the necessity to go over to the defensive, is already on us, and in addition all the gains which we made in the spring—such as they were—have been lost again.” Still, Erich Ludendorff, the German commander in chief, refused to accept this reality and rejected the advice of his senior commanders to pull back or begin negotiations.

Meanwhile, the Allies prepared for the war to stretch into 1919, not realizing victory was possible so soon. Thus, at a conference of national army commanders on July 24, Allied generalissimo Ferdinand Foch rejected the idea of a single decisive blow against the Germans, favoring instead a series of limited attacks in quick succession aimed at liberating the vital railway lines around Paris and diverting the attention and resources of the enemy rapidly from one spot to another.

According to Foch: “These movements should be exacted with such rapidity as to inflict upon the enemy a succession of blows….These actions must succeed each other at brief intervals, so as to embarrass the enemy in the utilization of his reserves and not allow him sufficient time to fill up his units.” The national commanders—John J. Pershing of the United States, Philippe Petain of France and Sir Douglas Haig of Britain—willingly went along with this strategy, which effectively allowed each army to act as its own entity, striking smaller individual blows to the Germans instead of joining together in one massive coordinated attack.

Haig’s part of the plan called for a limited offensive at Amiens, on the Somme River, aimed at counteracting a German victory there the previous March and capturing the Amiens railway line stretching between Mericourt and Hangest. The British attack, begun on the morning August 8, 1918, was led by the British 4th Army under the command of Sir Henry Rawlinson. The German defensive positions at Amiens were guarded by 20,000 men; they were outnumbered six to one by advancing Allied forces. The British—well assisted by Australian and Canadian divisions—employed some 400 tanks in the attack, along with over 2,000 artillery pieces and 800 aircraft.

By the end of August 8—dubbed “the black day of the German army” by Ludendorff—the Allies had penetrated German lines around the Somme with a gap some 15 miles long. Of the 27, 000 German casualties on August 8, an unprecedented proportion—12,000—had surrendered to the enemy.

Though the Allies at Amiens failed to continue their impressive success in the days following August 8, the damage had been done. “We have reached the limits of our capacity,” Kaiser Wilhelm II told Ludendorff on that “black day.” “The war must be ended.” The kaiser agreed, however, that this end could not come until Germany was again making progress on the battlefield, so that there would be at least some bargaining room. Even faced with the momentum of the Allied summer offensive—later known as the Hundred Days Offensive—the front lines of the German army continued to fight on into the final months of the war, despite being plagued by disorder and desertion within its troops and rebellion on the home front.