On March 21, 1918, a major offensive against Allied positions in the Somme River region of France began with five hours of bombardment from more than 9,000 pieces of German artillery. The poorly prepared British Fifth Army was rapidly overwhelmed and forced into retreat. For a week, the Germans pushed toward Paris, shelling the city from a distance of 80 miles with their long range gun called the “Kaiser Wilhelmgeschütz,” or as the Parisians called it, the "Big Bertha."
However, the poorly supplied German troops soon became exhausted, and the Allies halted the German advance as French artillery knocked out the German guns besieging Paris. On April 2, U.S. General John J. Pershing sent American troops down into the trenches to help defend Paris and repulse the German offensive. It was the first major deployment of U.S. troops in World War I. Several thousand American troops fought alongside the British and French in the Second Battle of Somme.
By the time the Somme offensive ended on April 4, the Germans had advanced almost 40 miles, inflicted some 200,000 casualties, and captured 70,000 prisoners and more than 1,000 Allied guns. However, the Germans suffered nearly as many casualties as their enemies and lacked the fresh reserves and supply boost the Allies enjoyed following the American entrance into the fighting.