North Korea's denial of involvement in the sinking of a South Korean navy ship from an "external explosion" -- a naval mine or torpedo -- might be true if the focus is on what North Korea has done recently [news stories, April 17 and 18].

But the South Korean corvette might well have struck a mine laid during the Korean War, when, with help from the Chinese, North Korea laid many thousands of mines along the coast of the Korean Peninsula.

More than 100,000 sea mines of all types and sizes are strewn throughout the world's oceans, seas and littorals. Mines laid in the North Sea in World War I still occasionally damage or sink fishing vessels, and in February, two World War II mines (one German, one British) were detected in the Kattegat Strait -- between the North and Baltic seas -- and rendered safe. A 2009 NATO mine assessment concluded there could be some 80,000 mines from both wars in the English Channel and the North and Baltic seas.

Since October 1945, mines have sunk or damaged nearly four times as many U.S. Navy warships as all other means of attack combined. There are growing concerns that terrorists are looking to naval mines and other underwater explosive devices to attack shipping or even naval forces -- as evidenced by the May 2008 sinking of a Sri Lankan naval vessel by a Tamil Tiger suicide diver.

Finally, this most recent tragedy underscores a mine warfare adage: Any ship can be a minesweeper . . . once.

Scott C. Truver, Severna Park