The British-built RMS Lusitania was made with the intention that it would serve as an armed merchant cruiser. They soon learned that it needed massive amounts of coal to run, and was deemed not economically sound for the role. It was, in turn, used for passenger travel across the Atlantic. Then in 1915, a German U-boat operating off the coast of Ireland fired a torpedo into RMS Lusitania, and the massive ocean liner sank in just 18 minutes. The attack was part of an unrestricted submarine warfare Germany waged against the UK. The attack left 1,198 people dead, including 128 Americans.