The ''Aggressive''-class minesweepers are a class of US-built
minesweeper
A minesweeper is a small warship designed to remove or detonate naval mines. Using various mechanisms intended to counter the threat posed by naval mines, minesweepers keep waterways clear for safe shipping.
History
The earliest known usage of ...
s. They are designated as ''MSO'' (Mine Sweeper Ocean), distinguishing them from the smaller coastal MSCs and inshore MSIs. Besides the
US Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
naval mine
A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any ve ...
s, by these vessels is performed in different ways:
*Sweeping proper, with an underwater cable cutting the mooring cables of moored mines. The mines then come to the surface and are destroyed by gunfire.
*Acoustic sweeping, with a towed device producing noise to trigger acoustic mines.
*Magnetic sweeping, with a towed device producing a magnetic field to trigger magnetic mines. To protect the minesweeper itself against magnetic mines, the hull and superstructure of the ship are made of wood. Other components are made of non-magnetic materials, and any magnetic materials are strictly controlled.
Construction and disposition
Of the 53 constructed for the United States Navy, 10 were built at Higgins Corp.,
J.M. Martinac Shipbuilding Corp.
The J. M. Martinac Shipbuilding Corporation was founded in 1924 by Joseph M. Martinac on the Thea Foss Waterway in Tacoma, Washington. It specialized in the construction of tugs, trawlers, purse seiners, ferries, naval patrol craft and power yach ...
,
Tacoma, Washington
Tacoma ( ) is the county seat of Pierce County, Washington, United States. A port city, it is situated along Washington's Puget Sound, southwest of Seattle, northeast of the state capital, Olympia, Washington, Olympia, and northwest of Mount ...
, 8 at Wilmington Boat Works Inc.,
Wilmington, California
Wilmington is a neighborhood in the Harbor region of Los Angeles, California, covering .
Featuring a heavy concentration of industry and the third-largest oil field in the continental United States, this neighborhood has a high percentage of L ...
, 6 at Luders Marine Construction Co. of
Stamford, Connecticut
Stamford () is a city in the U.S. state of Connecticut, outside of Manhattan. It is Connecticut's second-most populous city, behind Bridgeport. With a population of 135,470, Stamford passed Hartford and New Haven in population as of the 2 ...
, 4 at Broward Marine Inc,
Fort Lauderdale, Florida
Fort Lauderdale () is a coastal city located in the U.S. state of Florida, north of Miami along the Atlantic Ocean. It is the county seat of and largest city in Broward County with a population of 182,760 at the 2020 census, making it the tenth ...
, 4 at Martinolich Shipbuilding Co.,
San Diego
San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United States ...
, California, 3 at Burger Boat Company,
Manitowoc, Wisconsin
Manitowoc () is a city in and the county seat of Manitowoc County, Wisconsin, United States. The city is located on Lake Michigan at the mouth of the Manitowoc River. According to the 2020 census, Manitowoc had a population of 34,626, with ov ...
Antioch, California
Antioch is the third-largest city in Contra Costa County, California, United States. Located in the East Bay region of the San Francisco Bay Area along the Sacramento–San Joaquin River Delta. The city's population was 115,291 at the 2020 cens ...
, 2 at
Norfolk Naval Shipyard
The Norfolk Naval Shipyard, often called the Norfolk Navy Yard and abbreviated as NNSY, is a U.S. Navy facility in Portsmouth, Virginia, for building, remodeling and repairing the Navy's ships. It is the oldest and largest industrial facility tha ...
and 2 at Seattle Shipbuilding and Drydocking Co.,
Seattle
Seattle ( ) is a port, seaport city on the West Coast of the United States. It is the county seat, seat of King County, Washington, King County, Washington (state), Washington. With a 2020 population of 737,015, it is the largest city in bo ...
, Washington.
33 of the class were decommissioned before the mid-1970s. Four ex-USN ships were sold to the
Republic of China Navy
The Republic of China Navy (ROCN; ), also called the ROC Navy and colloquially the Taiwan Navy, is the maritime branch of the Republic of China Armed Forces (ROCAF).
The service was formerly commonly just called the Chinese Navy during World W ...
1994 and re-classed as s. They were still in active service in 2012. was decommissioned 30 September 1994 in Tacoma, Washington and was the last ''Aggressive''-class minesweeper in US Navy active service.
File:USS Conquest (MSO-488) mine detection sonar console.jpg, A crewman monitors a mine detection and classification sonar console aboard the ocean minesweeper USS ''Conquest''
File:USS Conquest (MSO-488) mine detection and classification console.jpg, A crewman monitors a mine detection and classification console aboard the ocean minesweeper USS ''Conquest''
File:Paravane aboard USS Engage (MSO-433).jpg, A paravane used for mine sweeping aboard USS ''Conquest''
File:USS Illusive (MSO-448) lowers an acoustical device during an exercise.jpg, USS ''Illusive'' lowers an acoustical device during an exercise.
File:USS Illusive (MSO-448) lowers an acoustical device for training 2.jpg, USS ''Illusive'' lowers a different acoustical device for training.
File:USS Illusive (MSO-448) deploys a mineweeping cable.jpg, USS ''Illusive'' deploys a mineweeping cable.
File:USS Constant (MSO-427) deploying the mag-tail.jpg, USS ''Constant'' deploying the "mag-tail", used to simulate the magnetic field of a vessel, are towed behind the ship to trigger magnetic mines.
File:Super Sea Rover aboard USS Conquest (MSO-488).jpg, A remote control mine-seeking system, Super Sea Rover, aboard USS ''Conquest''
File:USS Esteem (MSO-438) deploys a marker.jpg, USS ''Esteem'' deploys a marker, for marking mines or mine fields.