On what date did the German offensive of which the First Battle of Villers-Bretonneux was a part begin?
Spring Offensive The 1918 Spring Offensive or Kaiserschlacht ("Kaiser's Battle"), also known as the Ludendorff Offensive, was a series of German attacks along the Western Front during the First World War, beginning on 21 March 1918, which marked the deepest advances by either side since 1914. The Germans had realised that their only remaining chance of victory was to defeat the Allies before the overwhelming human and matériel resources of the United States could be fully deployed. They also had the temporary advantage in numbers afforded by the nearly 50 divisions freed by the Russian surrender (the Treaty of Brest-Litovsk).
Hindenburg Line The Hindenburg Line ("Siegfriedstellung" or Siegfried Position) was a German defensive position of World War I, built during the winter of 1916–1917 on the Western Front, from Arras to Laffaux, near Soissons on the Aisne. In 1916, the German offensive at the Battle of Verdun had been a costly failure. The Anglo-French offensive at the Battle of the Somme had forced a defensive battle on the Germans, leaving the western armies ("Westheer") exhausted. On the Eastern Front, the Brusilov Offensive had inflicted huge losses on the Austro-Hungarian armies in Russia and forced the Germans to take over more of the front. The declaration of war by Romania had placed additional strain on the German army and war economy. Construction of the Hindenburg Line in France was begun by the Germans in September 1916, to make a retirement from the Somme front possible, to counter an anticipated increase in the power of Anglo-French attacks in 1917.