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MSO 422 Aggressive 


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These ocean going minesweepers were designed to counter North Korean mining during the Korean War. They were capable of sweeping for moored and bottom contact, magnetic and acoustic mines. During the 1987-88 Persian Gulf escort missions, active and reserve MSO's were dispatched to the Gulf. Both ships and crews performed extremely well in very demanding conditions, clearing hundreds of mines from the international waterway.

During the Cold War the US mine warfare concept was designed around a European war scenario which relied on North Atlantic Treaty Organization (NATO) allies to participate substantially in mine warfare operations. The Navy's MCM capabilities in the Persian Gulf included the surface mine countermeasures (SMCM) capabilities of three 30-year-old USS Aggressive and USS Acme (MSO 422 and 508) class minesweepers. These minesweepers used the AN/SQQ-14 MCM sonar to detect bottom and moored mines and mechanical minesweeping gear to cut mine cables.

All units of this class have been stricken, with some to be disposed of by the Security Assistance Program (SAP) for cash sale and others to be sold by the Defense Reutilization and Marketing Service (DRMS) for scrapping. Some units were stricken and sold, but the Contractor defaulted and the ship was repossessed by the Navy to be resold.

Specifications  Return to Top

Builders Various companies, including:
Colberg Boatworks, Stockton CA
Higgins Incorporated
J.M. Martinac Shipbuilding Corporation
Martinolich Shipbuilding Company
Wilmington Boat Works
Displacement 853 tons (full load)
Length 172 feet
Beam 35 feet
Max Speed 15 knots
Power Plant 4 - Aluminum block Diesels; 2 shafts, 2,400 bhp
Aircraft None
Armament 2 - .50 cal twin machine guns
Complement Active: 77: 7 officer, 70 enlisted;
NRF: 57: 5 officer, 52 enlisted plus 25 reserve
Unit Operating Cost
Annual Average
$3,500,000 [source: [FY1996 VAMOSC]

Ships  Return to Top

Name Number Builder Homeport Ordered Commissioned Decommissioned
Agile MSO-421          
Aggressive MSO-422          
Bold MSO-424          
Bulwark MSO-425          
Conflict MSO-426          
Constant MSO-427   San Diego   09 Sep 1954 30 Sep 1992
Dash MSO-428          
Detector MSO-429          
Direct MSO-430          
Dominant MSO-431          
Dynamic MSO-432          
Engage MSO-433 Colberg Mayport   29 Jun 1954 30 Dec 1991
Embattle MSO-434          
Endurance MSO-435          
Energy MSO-436          
Enhance MSO-437   Tacoma   16 Apr 1955 13 Dec 1991
Esteem MSO-438 Martinolich Seattle 07 Aug 1951 10 Sep 1955 30 Sep 1991
Excel MSO-439   San Francisco   24 Feb 1955 30 Sep 1992
Exploit MSO-440   Newport   31 Mar 1954 16 Dec 1993
Exultant MSO-441 Higgins Charleston   22 Jun 1954 30 Jun 1993
Fearless MSO-442 Higgins Charleston   22 Sep 1954 31 Oct 1990
Fidelity MSO-443          
Firm MSO-444          
Force MSO-445          
Fortify MSO-446   Little Creek   16 Jul 1954 31 Aug 1992
Guide MSO-447          
Illusive MSO-448   Mayport   14 Nov 1953 30 Mar 1990
Impervious MSO-449   Mayport   15 Jul 1954 12 Dec 1991
Implicit MSO-455   Tacoma   10 Mar 1954 30 Sep 1994
Inflict MSO-456   Little Creek   11 May 1954 30 Mar 1990
Loyalty MSO-457          
Lucid MSO-458          
Nimble MSO-459          
Observer MSO-461          
Pinnacle MSO-462          
Pivot MSO-463          
Pluck MSO-464 Wilmington San Diego 31 Mar 1952 11 Aug 1954 29 Nov 1990
Prime MSO-466          
Reaper MSO-467          
Skill MSO-471          
Vigor MSO-473          
Vital MSO-474          
Conquest MSO-488 JM Martinac Seattle 29 Dec 1952 08 Jul 1955 29 Jun 1994
Gallant MSO-489 JM Martinac San Francisco 29 Dec 1952 14 Sep 1955 29 Apr 1994
Leader MSO-490 JM Martinac Charleston 29 Dec 1952 16 Nov 1955 18 Mar 1992
Persistent MSO-491          
Pledge MSO-492 JM Martinac Seattle 29 Dec 1952 20 Apr 1956 31 Jan 1994
Sturdy MSO-494          
Swerve MSO-495          
Venture MSO-496          
Ships not otherwise detailed were built in the 1950s and stricken in the 1970s.
This class is rather poorly attested in the Naval Vessel Register - MINESWEEPER,OCEAN section.

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