Operation Michael was a First World War German military operation that began the Spring Offensive on 21 March 1918.
It was launched from the Hindenburg Line, in the vicinity of Saint-Quentin, France. Its goal was to break through the Allied lines and advance in a north-west direction and seize the Channel ports which supplied the British Expeditionary Force (BEF) and drive the BEF into the sea. Just two days into the operation, Ludendorff changed his plan, and pushed for an offensive due west along the whole of the British front north of the Somme. This was designed to separate the French and British Armies and crush the British forces by pushing them into the sea. The offensive ended at Villers-Bretonneux, a little to the east of the key Allied communications centre of Amiens, where the Entente managed to halt the German advance. The German advance stalled largely through very heavy casualties, an inability to maintain supplies to the advancing troops and the arrival of Entente reserves. Since much of the territory involved consisted of the shell-torn wilderness left by the 1916 Battle of the Somme it was known to some as the 1918 Battle of the Somme, and to the French as the Second Battle of Picardy (French: 2ème Bataille de Picardie).
The German armies involved were the Seventeenth Army under Otto von Below, the Second Army under Georg von der Marwitz and the Eighteenth Army under Oskar von Hutier, with a Corps (Gruppe Gayl) from the Seventh Army supporting Hutier's attack. Although the British had learned the approximate time and location of the offensive, the weight of the attack and of the preliminary bombardment was an unpleasant surprise. The Germans were also fortunate in that the morning of the attack was foggy, allowing the stormtroopers leading the attack to penetrate deep into the British positions undetected.
By the end of the first day the British had lost nearly 20,000 dead and 35,000 wounded, and the Germans had broken through at several points on the front of the British Fifth Army. After two days Fifth Army was in full retreat. As they fell back, many of the isolated "redoubts" were left to be surrounded and overwhelmed by the following German infantry. The right wing of Third Army became separated from the retreating Fifth Army, and also retreated to avoid being outflanked.