Germany sank the RMS Lusitania because they believed it was carrying munitions to Britain, which was their enemy in World War I. German U-boats (submarines) were deployed in the North Atlantic Ocean to intercept and destroy any ships carrying supplies to the British war effort. The Lusitania was a British ocean liner that was sunk on May 7, 1915, by a German U-boat off the coast of Ireland. The sinking of the Lusitania resulted in the deaths of 1,198 people, including 128 Americans, and was a significant factor in the United States entering World War I.