This work led to their induction into the National Inventors Hall of Fame in 2014. Post–World War II Because of improved submarine strength and speed, torpedoes had to be given improved warheads and better motors. During the Cold War torpedoes were an important asset with the advent of nuclear-powered submarines, which did not have to surface often, particularly those carrying strategic nuclear missiles. Several navies have launched torpedo strikes since World War II, including: During the Korean War the United States Navy successfully attacked a dam with air-launched torpedoes. Israeli Navy fast attack craft crippled the American electronic intelligence vessel USS Liberty with gunfire and torpedoes during the 1967 Six-Day War, resulting in the loss of 46 crew. A Pakistan Navy sank the Indian frigate on 9 December 1971 during the Indo-Pakistani War of 1971, with the loss of over 18 officers and 176 sailors. The British Royal Navy nuclear attack submarine sank the Argentine Navy light cruiser with two Mark 8 torpedoes during the Falklands War with the loss of 323 lives. During the Lebanon War, an unnamed Israeli submarine torpedoed and sank the Lebanese coaster Transit, which was carrying 56 Palestinian refugees to Cyprus, in the belief that the vessel was evacuating anti-Israeli militias. The ship was hit by two torpedoes, managed to run aground but eventually sank. There were 25 dead, including her captain. The Israeli Navy disclosed the incident in November 2018. The Croatian Navy disabled the Yugoslav patrol boat PČ-176 Mukos with a torpedo launched by Croatian naval commandos from an improvised device during the Battle of the Dalmatian channels on 14 November 1991, in the course of the Croatian War of Independence. Three members of the crew were killed. The stranded boat was later recovered by Croatian trawlers, salvaged and put in service with the Croatian Navy as OB-02 Šolta. On 26 March 2010 the South Korean Navy ship ROKS Cheonan was sunk with the loss of 46 personnel. A subsequent investigation concluded that the warship had been sunk by a North Korean torpedo fired by a midget submarine. Energy sources Compressed air The Whitehead torpedo of 1866, the first successful self-propelled torpedo, used compressed air as its energy source. The air was stored at pressures of up to and fed to a piston engine that turned a single propeller at about 100 rpm. It could travel about at an average speed of .