US and South Korean naval forces are staging their biggest-ever joint exercise off the tense Korean peninsula, days after the North launched a deadly artillery strike against the South.
Leading the four-day show of firepower until Wednesday in the Yellow Sea is nuclear-powered aircraft carrier the USS George Washington and its battle group, joined by a flotilla of South Korean destroyers and other warships.
The Pentagon has said the manoeuvre in international waters is "defensive in nature", was planned months before North Korea's attack and is not directed at China which opposes the drill.
But Washington has also said that it will act as a "deterrent" to the volatile regime of Kim Jong-Il.
The centrepiece of the US Navy strike force is the 97,000-ton George Washington, which can carry 80 aircraft on its 1.8 hectare (4.5 acre) flight deck and on this drill has a crew of 5,500 service personnel.