# Aggressive-class minesweeper

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 | 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 | 424 | Norfolk Naval Shipyard | 1953-1971 | Sold for scrap 1981 | |
| Bulwark | 425 | Norfolk Naval Shipyard | 1953-1971 | Sold for scrap 1980 | |
| Conflict | 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 | 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 | 496 | Broward Marine Inc, Fort Lauderdale, Florida | 1958-1971 | Sold for scrap 1978 | |
| MSO-497 | 497 | Cancelled, never built | Cancelled, never built | Cancelled, never built | Cancelled, never built |