The German spring offensive, or Kaiserschlacht, 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. Following American entry into the war in April 1917, the Germans decided that their only remaining chance of victory was to defeat the Allies before the United States could ship soldiers across the Atlantic and fully deploy its resources. The German Army had gained a temporary advantage in numbers as nearly 50 divisions had been freed by the Russian defeat and withdrawal from the war with the Treaty of Brest-Litovsk.

The German Empire, also referred to as Imperial Germany, the Second Reich or simply Germany, was the period of the German Reich from the unification of Germany in 1871 until the November Revolution in 1918, when the German Reich changed its form of government from a monarchy to a republic.