Aggressive-class minesweeper

	USS Constant (MSO-427) in 1988
Class overview
Name	Aggressive class
Operators	United States Navy ; Republic of China Navy ; Belgian Navy ; Royal Norwegian Navy ; Royal Netherlands Navy ; Philippine Navy ;
Subclasses	Onversaagd class
In commission	1953–Present
Completed	53
Active	1
Retired	52
Preserved	2
General characteristics
Type	Minesweeper
Displacement	853 tons (full load)
Length	172 ft (52 m)
Beam	35 ft (11 m)
Draft	10 ft (3 m)
Propulsion	4 × aluminum block Waukesha diesels, 2,400 bhp (1,800 kW); 2 × shafts; 2 × controllable pitch propellers;
Speed	14 knots (26 km/h; 16 mph)
Complement	7 officers, 70 enlisted
Sensors and ; processing systems	AN/SQQ-14 mine hunting sonar
Armament	1 × twin 20 mm gun; 2 × .50 cal (12.7 mm) twin machine guns;

Last updated March 21, 2023

The Aggressive-class minesweepers are a class of US-built minesweepers. They are designated as MSO (Mine Sweeper Ocean), distinguishing them from the smaller coastal MSCs and inshore MSIs. Besides the US Navy, this class of vessels has also been used by the Belgian Navy and the Norwegian Navy, among others.

Background

Minesweeping, or the disposal of naval mines, 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., New Orleans, Louisiana, 9 at J.M. Martinac Shipbuilding Corp., Tacoma, Washington, 8 at Wilmington Boat Works Inc., Wilmington, California, 6 at Luders Marine Construction Co. of Stamford, Connecticut, 4 at Broward Marine Inc, Fort Lauderdale, Florida, 4 at Martinolich Shipbuilding Co., San Diego, California, 3 at Burger Boat Company, Manitowoc, Wisconsin, 3 at Colberg Boat Works, Stockton, California, 2 at Fulton Shipyard, Antioch, California, 2 at Norfolk Naval Shipyard and 2 at Seattle Shipbuilding and Drydocking Co., Seattle, Washington.

33 of the class were decommissioned before the mid-1970s. Four ex-USN ships were sold to the Republic of China Navy 1994 and re-classed as Yung Yang-class minesweepers. They were still in active service in 2012. USS Implicit was decommissioned 30 September 1994 in Tacoma, Washington and was the last Aggressive-class minesweeper in US Navy active service.

A crewman monitors a mine detection and classification sonar console aboard the ocean minesweeper USS Conquest
A crewman monitors a mine detection and classification console aboard the ocean minesweeper USS Conquest
A paravane used for mine sweeping aboard USS Conquest
USS Illusive lowers an acoustical device during an exercise.
USS Illusive lowers a different acoustical device for training.
USS Illusive deploys a mineweeping cable.
USS Constant deploying the "mag-tail", used to simulate the magnetic field of a vessel, are towed behind the ship to trigger magnetic mines.
A remote control mine-seeking system, Super Sea Rover, aboard USS Conquest
USS Esteem deploys a marker, for marking mines or mine fields.

Units

Ship Name	Hull no.	Builder	Commission– Decommission	Fate	Link
Aggressive ^[1]	422	Luders Marine Construction Co. of Stamford, Connecticut	1953–1971	Sold for scrap 1980
Avenge	423	Luders Marine Construction Co. of Stamford, Connecticut	1954-1970	Destroyed by fire, sold for scrapping 1969
Bold ^[2]	424	Norfolk Naval Shipyard	1953-1971	Sold for scrap 1981
Bulwark ^[3]	425	Norfolk Naval Shipyard	1953-1971	Sold for scrap 1980
Conflict ^[4]	426	Fulton Shipyard, Antioch, California	1954-1973	Sold for scrap 1973
Constant	427	Fulton Shipyard, Antioch, California	1954-1992	Sold for scrap 2001	Naval Vessel Register
428 - 431 were US Dash-class minesweepers
Dynamic	432	Colberg Boat Works, Stockton, California	1953-1971	Sold or loaned to Spain as Guadalete M41, 1971.	Naval Vessel Register
Engage	433	Colberg Boat Works, Stockton, California	1953-1991	Scrapped 2002	Naval Vessel Register
Embattle	434	Colberg Boat Works, Stockton, California	1954-1972	Sold to be scrapped 1976, privately held until scrapped by USACE in 1993.	Naval Vessel Register
Endurance	435	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1954-1972	Sold for scrap 1973	Naval Vessel Register
Energy	436	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1954-1972	Loaned to Philippines 1972 Sold for scrap 1977	Naval Vessel Register
Enhance	437	Martinolich Shipbuilding Co., San Diego, California	1955-1970 1971-1991	Sold for scrap 2000	Naval Vessel Register
Esteem	438	Martinolich Shipbuilding Co., San Diego, California	1955-1970 1971-1991	Sold for scrap 2000	Naval Vessel Register
Excel	439	Higgins Corp., New Orleans, Louisiana	1955-1992	Sold for scrap 2000	Naval Vessel Register
Exploit	440	Higgins Corp., New Orleans, Louisiana	1954-1993	Sold for scrap 2002	Naval Vessel Register
Exultant	441	Higgins Corp., New Orleans, Louisiana	1954-1993	Sold for scrap 2002	Naval Vessel Register
Fearless	442	Higgins Corp., New Orleans, Louisiana	1954-1990	Sold for scrap 1992	Naval Vessel Register
Fidelity	443	Higgins Corp., New Orleans, Louisiana	1955-1989	Sold for scrap 1990	Naval Vessel Register
Firm	444	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1954-1972	Loaned to Philippines 1972 Scrapped 1977	Naval Vessel Register
Force	445	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1955-1973	Sunk after a fire	Naval Vessel Register
Fortify	446	Seattle Shipbuilding and Drydocking Co., Seattle, Washington	1954-1992	Scrapped 2002	Naval Vessel Register
Guide	447	Seattle Shipbuilding and Drydocking Co., Seattle, Washington	1955-1972	Sold for scrap 1973	Naval Vessel Register
Illusive	448	Martinolich Shipbuilding Co., San Diego, California	1953-1990	Sold for scrap 1993	Naval Vessel Register
Impervious	449	Martinolich Shipbuilding Co., San Diego, California	1954-1991	Scrapped 2002	Naval Vessel Register
450 - 454 built at Bellingham Shipyards Co., Bellingham, Washington for France, not necessarily Aggressive-class ships.
Implicit	455	Wilmington Boat Works Inc., Wilmington, California	1954-1994	Sold to Taiwan 1994	Naval Vessel Register
Inflict	456	Wilmington Boat Works Inc., Wilmington, California	1954-1990	Sold for scrap 1992	Naval Vessel Register
Loyalty	457	Wilmington Boat Works Inc., Wilmington, California	1954-1972	Sold for scrap 1973	Naval Vessel Register
Lucid	458	Higgins Corp., New Orleans, Louisiana	1955-1970	Sold for scrap 1976 Currently being restored by the Stockton Historical Maritime Museum as a museum ship	Naval Vessel Register
Nimble	459	Higgins Corp., New Orleans, Louisiana	1955-1970	Sold for scrap 1981	Naval Vessel Register
Notable	460	Higgins Corp., New Orleans, Louisiana	1955-1970	Sold for scrap 1971	Naval Vessel Register
Observer	461	Higgins Corp., New Orleans, Louisiana	1955-1972	Sold for scrap 1979	Naval Vessel Register
Pinnacle	462	Higgins Corp., New Orleans, Louisiana	1955-1970	Sold for scrap 1978	Naval Vessel Register
Pivot	463	Wilmington Boat Works Inc., Wilmington, California	1954-1971	Initially loaned then sold to Spain as Guadalmedina M42, 1974. Decommissioned by Spain 2001.	Naval Vessel Register
Pluck	464	Wilmington Boat Works Inc., Wilmington, California	1954-1990	Sold for scrap 1992	Naval Vessel Register
Prestige	465	Wilmington Boat Works Inc., Wilmington, California	1954-1958	Grounded and sunk, 1958 in the Naruto Strait
Prime	466	Wilmington Boat Works Inc., Wilmington, California	1954-1970	Sold for scrap 1976	Naval Vessel Register
Reaper	467	Wilmington Boat Works Inc., Wilmington, California	1954-1972	Sold for scrap 1976	Naval Vessel Register
Rival	468	Luders Marine Construction Co. of Stamford, Connecticut	1954-1970	Sold for scrap 1971	Naval Vessel Register
Sagacity	469	Luders Marine Construction Co. of Stamford, Connecticut	1955-1970	Grounded at Charleston Harbor then sold for scrap 1970.
Salute	470	Luders Marine Construction Co. of Stamford, Connecticut	1955-1970	Sold for scrap 1971	Naval Vessel Register
Skill	471	Luders Marine Construction Co. of Stamford, Connecticut	1950-1970	Sold for scrap 1979, scrapped 1983.	Naval Vessel Register
Valor	472	Burger Boat Company, Manitowoc, Wisconsin	1954-1970	Sold for scrap 1971	Naval Vessel Register
Vigor	473	Burger Boat Company, Manitowoc, Wisconsin	1954-1972	Sold to Spain as Guadiana M44, 1972. Scrapped by Spain after 1999.	Naval Vessel Register
Vital	474	Burger Boat Company, Manitowoc, Wisconsin	1955-1972	Sold for scrap 1979	Naval Vessel Register
475 - 487 built for France, Portugal, Spain, Belgium and the Netherlands, not necessarily Aggressive-class ships.
Conquest	488	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1955-1970 1971-1994	Sold to Taiwan 1994 and decommissioned in 2020.	Naval Vessel Register
Gallant	489	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1955-1994	Sold to Taiwan 1994 and decommissioned in 2013.	Naval Vessel Register
Leader	490	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1955-1970 1971-1991/92	Sold for scrap 1994	Naval Vessel Register
Persistent	491	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1956-1971	Initially loaned in 1971 then sold to Spain as Guadalquivir M43	Naval Vessel Register
Pledge ^[5]	492	J. M. Martinac Shipbuilding Corp., Tacoma, Washington	1956-1994	Sold to Taiwan 1994 and decommissioned 2021.	Naval Vessel Register
Stalwart	493	Broward Marine Inc, Fort Lauderdale, Florida	1956-1966	Caught fire pier side at San Juan, Puerto Rico, sunk 1966. Later raised and sunk as an artificial reef.
Sturdy	494	Broward Marine Inc, Fort Lauderdale, Florida	1957-1971	Sold for scrap 1978	Naval Vessel Register
Swerve	495	Broward Marine Inc, Fort Lauderdale, Florida	1957-1971	Sold for scrap 1978	Naval Vessel Register
Venture ^[6]	496	Broward Marine Inc, Fort Lauderdale, Florida	1958-1971	Sold for scrap 1978
MSO-497	497	Cancelled, never built

Related Research Articles

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.

USS Gallant (MSO-489), an Aggressive-class minesweeper, was the second ship of the United States Navy to be named Gallant. The ship served in the US Navy from 1954 until 1994, when it was sold to Taiwan under the Security Assistance Program and renamed to Yung Ku.

Mine Squadron 7, is the designation for a United States Navy minelaying and retrieval command and unit. COMINRON SEVEN was assigned to the United States Pacific Fleet from some time before 1943 until the unit's decommissioning in 1968. The word Commander in the unit's nomenclature refers both the entire unit, the headquarters section, and to the actual commanding officer.

Destroyer minesweeper was a designation given by the United States Navy to a series of destroyers that were converted into high-speed ocean-going minesweepers for service during World War II. The hull classification symbol for this type of ship was "DMS." Forty-two ships were so converted, beginning with USS Dorsey (DD-117), converted to DMS-1 in late 1940, and ending with USS Earle (DD-635), converted to DMS-42 in mid-1945. The type is now obsolete, its function having been taken over by purpose-built ships, designated as "minesweeper (high-speed)" with the hull classification symbol MMD.

USS Lucid (AM-458/MSO-458) is an Aggressive-class minesweeper acquired by the U.S. Navy for the task of removing naval mines that had been placed in the water to prevent the safe passage of ships. She was launched soon after the Korean War, sailed on five Western Pacific (Westpac) cruises and served four tours in Vietnam during the Vietnam War. Lucid was decommissioned at the end of 1970 and placed in mothballs after only 15 years of service, as the Vietnam War was winding down and there was no longer a need for a large fleet of minesweepers. She was purchased by civilians and served as a houseboat for ten years, before being sold again in 1986 and used as a warehouse by a scrap metal dealer on Bradford Island, in the Sacramento–San Joaquin River Delta. The scrap metal dealer was murdered in 2004 over a property dispute, and in 2005, Lucid was acquired by a foundation seeking to save a ship of its class. In 2011, the ship was moved to the Stockton Maritime Museum to be restored for use as a museum ship. Lucid is the last Aggressive-class minesweeper afloat in the United States.

USS Firm (AM-444/MSO-444) was an Aggressive-class minesweeper in the United States Navy.

USS Conquest (MSO-488) was an Agile-class minesweeper in the United States Navy.

USS Energy (AM-436/MSO-436) was an Aggressive-class minesweeper acquired by the U.S. Navy for the task of removing mines that had been placed in the water to prevent the safe passage of ships.

USS Enhance (AM-437/MSO-437) was an Aggressive-class minesweeper acquired by the U.S. Navy for the task of removing mines that had been placed in the water to prevent the safe passage of ships.

USS Illusive (AM-448/MSO-448) was an Agile-class minesweeper acquired by the U.S. Navy for the task of removing mines that had been placed in the water to prevent the safe passage of ships.

USS Impervious (AM-449/MSO-449) was an Agile-class minesweeper acquired by the U.S. Navy for the task of removing mines that had been placed in the water to prevent the safe passage of ships.

USS Inflict (AM-456/MSO-456) was an Aggressive-class minesweeper acquired by the U.S. Navy for the task of removing mines that had been placed in the water to prevent the safe passage of ships.

USS Leader (AM-490/MSO-490) was an Agile-class minesweeper acquired by the U.S. Navy for the task of removing mines that had been placed in the water to prevent the safe passage of ships.

USS Persistent (AM-491/MSO-491) was an Aggressive-class minesweeper acquired by the U.S. Navy for the task of removing mines that had been placed in the water to prevent the safe passage of ships.

USS Pledge (MSO-492) was an Aggressive-class minesweeper acquired by the U.S. Navy.

USS Stalwart (AM-493/MSO-493) was an Aggressive-class minesweeper acquired by the U.S. Navy for the task of removing mines that had been placed in the water to prevent the safe passage of ships.

USS Adroit (AM-509/MSO-509) was an Acme-class minesweeper acquired by the U.S. Navy for the task of removing mines that had been placed in the water to prevent the safe passage of ships.

Avenger-class mine countermeasures ships are a class of 14 ships constructed for the United States Navy from 1987 to 1994, designed to clear mines from vital waterways. The ships have the hull designator MCM.

Operation End Sweep was a United States Navy and United States Marine Corps operation to remove naval mines from Haiphong harbor and other coastal and inland waterways in North Vietnam between February and July 1973. The operation fulfilled an American obligation under the Paris Peace Accord of January 1973, which ended direct American participation in the Vietnam War. It also was the first operational deployment of a U.S. Navy air mine countermeasures capability.

The Agile-class minesweepers are a class of US-built ocean-going minesweepers. 58 ships were built for the United States Navy, 35 ships were built for the allied NATO navies of Belgium, France, Italy, the Netherlands, Norway and Portugal. 13 ships were later transferred to Belgium, Spain, Taiwan, the Philippines and Uruguay.

References

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[1] AGGRESSIVE (MSO 422)

[2] Naval Vessel Register

[3] Naval Vessel Register

[4] Naval Vessel Register

[5] Naval Vessel Register

[6] Naval Vessel Register

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