In 1950 during the Korean War, a minefield in Wonsan harbor inspired the opening quote by Admiral Smith. That minefield delayed the planned landing by over a week, while 250 ships steamed back and forth outside the harbor. The US Navy lost four minesweepers in the process of clearing it, and several other ships were also sunk or damaged. Naval mines were first used effectively in the Russo-Japanese war of 1904, where they were decisive in spite of being primitive contact mines. With improved sensors, naval mines have been used effectively in every significant naval conflict since then (Hartmann, 1979). Most of the damage done to the US Navy since World War II has been due to mines (National Research Council, 2001).