South Korea and the US - with which it has a long military relationship - had already been conducting large-scale military exercises, following the apparent torpedoing of a South Korean warship by the North on 26 March, which killed 46 south Korean sailors.

BBC: New South Korea exercises to test border tension

The military thinking behind a cruiser such as the Ticonderoga class is to create an offensive warship that will also provide defensive firepower for a carrier group or amphibious operation under air or sea attack.

BBC: News | In Depth | Military Fact Files