[ame="http://www.youtube.com/watch?v=9nZhtJyvqRs"]http://www.youtube.com/watch?v=9nZhtJyvqRs[/ame] The United States and South Korea have begun a 4-day joint naval exercise in the Sea of Japan, despite threats of retalliation from North Korea. South Korea's Defense Ministry said the drill began as the nuclear aircraft carrier USS George Washington left the southern port of Pusan at 7 AM on Sunday. The 2 countries are conducting the drill following the sinking of a South Korean warship in March near the North Korean border. An international investigation determined that a North Korean torpedo sank the ship. About 200 fixed-wing aircraft, including state-of-the-art US F-22 Raptor stealth fighters, vessels, and submarines are believed to be taking part in the drill. South Korea and the US also plan to hold annual joint drills called Ulji Freedom Guardian for 11 days next month. On Saturday, North Korea threatened to use its nuclear deterrent in a retaliatory "sacred war" in response to the ongoing exercise.