The RMS Lusitania was a passenger ship that was sunk by a German U-boat in 1915, killing 1,198 people onboard including many passengers. While it was mainly a passenger ship, it was found to be secretly carrying ammunition for Allied soldiers. This controversial cargo, along with the large loss of American lives, contributed to the United States entering World War 1. The sinking occurred relatively close to the Irish coast and the ship sank very quickly after being hit by two torpedoes, one of which caused a cargo explosion.