MINESWEEPING, the systematic clearance of mines from an area where submarines, surface ships, or aircraft have planted them. Most minesweeping involves towing various devices behind a ship: serrated wires to cut the mooring lines of contact mines to bring them to the surface; noisemakers to detonate acoustic mines; and cables with a pulsating current to set off magnetic mines. No method for sweeping pressure mines exists, but generally they are set to sterilize themselves after a certain period, when they become harmless.
Minesweeping is a tedious and dangerous operation. During the Civil War, Union forces dragged for Confederate mines with chains strung between boats but failed to make mined areas completely safe. After World War I, during which the United States and Great Britain laid some 56,000 mines in a stretch of the North Sea 230 miles long and from fifteen to thirty-five miles wide, minesweepers spent months incompletely clearing the mines.
During World War II, combatants laid an estimated 500,000 mines in all the world's oceans. In European waters alone, more than 1,900 minesweepers spent approximately two years clearing mines. American minesweepers cleared some 17,000 square miles of water in the Japanese area.
No extensive mining operations have been conducted since World War II, although the North Koreans laid mines off both Korean coasts during the Korean War, and the U.S. Air Force dropped mines in Haiphong harbor during the Vietnam War. Minesweepers subsequently cleared both areas. Helicopters, which are faster, safer, and more efficient than ships, have virtually taken over minesweeping.
Lott, Arnold S. Most Dangerous Sea; A History of Mine Warfare and an Account of U.S. Navy Mine Warfare Operations in World War II and Korea. Annapolis, Md.: U.S. Naval Institute, 1959.
Marolda, Edward J., ed. Operation End Sweep: A History of Minesweeping Operations in North Vietnam. Washington, D.C.: Naval Historical Center, Department of the Navy, 1993.
Arnold S.Lott/c. w.