Somme, river, northern France. It rises near St-Quentin, flows north-west past Amiens, and after a course of 241 km (150 mi) empties into the English Channel near St-Valéry. It was the scene of major battles in World War I; the huge allied offensive of July 1916 that became one of the bloodiest battles of history with over 1 million casualties, and the German offensive of March 1918, with a further 380,000 casualties.