They towed the Cold War mine line: The Agile/Aggressive/Dash-class MSOs
The U.S. Navy has a long history of mine sweeping, having lost the first modem ships to those infernal torpedoes in the Civil War. As a byproduct of Mr. Roosevelt’s Great North Sea Mine Barrage of the Great War, the Navy commissioned their first class of minesweepers, the Lapwing or “Old Bird” type vessels which lingered into WWII, followed by 1930s-era 147-foot three-ship Hawk-class and the much larger 220-foot Raven and Auk-classes early in the first days of that second great international hate.
Then came the 123-ship Admirable (AM-136)-class of 180-foot/950-ton vessels built during WWII– many of which remained in hard service through Korea before being passed on to allied nations.
With the lessons learned from that conflict, in which the Koreans used literally thousands of Soviet, Chinese and leftover Japanese mines up and down the coastline, a class of MSO (Mine Sweeper Ocean), sweepers was placed on order during that police action, with class leader USS Agressive (MSO-422) laid down at Luders Marine in Stamford, Connecticut 25 May 1951 and commissioned just weeks after the cease fire in 1953
At some 867-tons (fl) and 172-foot overall, they were roughly the same size as the steel-hulled minesweepers Admirable-class ships they were replacing, but they had a bunch of new tricks up their sleeve including using laminated wood construction with bronze and stainless steel fittings and to minimize their magnetic signature.
The main propulsion plant consisted of four Packard 1D1700 non magnetic diesel engines driving twin controllable pitch propellers (CRP). This was one of the earliest CRP installations in the navy.
They were also fitted with a UQS-1 mine-locating sonar, an important next step in minehunting.
Thus equipped, they could sweep moored mines with Oropesa (“O” Type) gear, magnetic mines with a Magnetic “Tail” supplied by three 2500 ampere mine sweeping generators, and acoustic mines by using Mk4(V) and A Mk6 (B) acoustic hammers.
Their armament, when compared to the Admirable-class steel hulls they replaced, was much lighter, consisting of a single Bofors 40mm/60 gun forward and two .50 cals. It should be pointed out the WWII sweepers carried a 3″/50, 4x Bofors, 6x20mm Oerlikons, Hedgehog ASW mortars plus depth charge racks and projectors on a hull roughly the same size.
Some 53 hulls were completed by 1958 by a host of small domestic yards for the U.S. Navy (Luders, Bellingham, Higgins, etc) that specialized in wooden vessels, and often had created PT-boats and sub-chasers during WWII. In addition to this, 15 were built for France, four for Portugal, six for Belgium, two for Norway, one of Uruguay, four for Italy, and six for Holland. The design was truly an international best-seller and in some cases the last hurrah for several of these small yards.
In U.S. service, they were quickly put to work everywhere from the Med to the South China Sea, performing general yeoman tasks for the fleet itself, participating in mine exercises and running sweeping ops in areas that still had the occasional WWII-era contact mine bobbing around. In addition, they helped with missile and torpedo tests, harbor defense exercises, acoustic ranging experiments, noise reduction experiments, located downed aircraft, performed special operations in 1962 during the nuclear tests in the Pacific Ocean, were instrumental in the Palomares hydrogen bombs incident, performed midshipman training cruises to the Caribbean, made repairs to cables and helped in the recovering of boilerplate and capsules for the Mercury and Gemini NASA programs.
Their shallow draft (10-feet in seawater) made them ideal for getting around littorals as well as going to some out of the way locales that rarely see Naval vessels. USS Leader (MSO-490) and USS Excel (MSO 439) became the first U.S. warships ever to visit the Cambodian capital of Phnom Penh when they completed the 180-mile transit up the Mekong River on 27 August 1961, a feat not repeated until 2007. USS Vital (MSO-474) ascended the Mississippi River in May 1967 to participate in the Cotton Carnival at Memphis, Tennessee.
USS Gallant (MSO-489) was used in 1966 for the filming of the Elvis Presley film, Easy Come, Easy Go.
Vietnam is where the class really shined, arriving early to the conflict, taking part in the party, and then sticking around for the clean up afterward.
As early as 1962, USS Fortify (MSO-446) was deployed off the coast of South Vietnam with her minesweeping gear removed and an electronic countermeasures “box” was installed on the fantail. The ship was involved in monitoring and intercepting Viet Cong radio transmissions, vectoring RVN gunboats to interdict large junks coming down the coast from the North that were suspected of furnishing arms and ammunition to cadres in the south. This led to some near-misses with NVA torpedo boats even before the Gulf of Tonkin incident.
Many of the class participated in Operation Market Time (11 March 1965 to December 1972) in an effort to stop the flow of supplies from North Vietnam into the south by sea. According to Navy reports, “The Tonkin Gulf Yacht Club” was very successful, but received little credit. Eventually all the supply routes at sea became non-existent, which forced the North Vietnamese to use the Ho Chi Minh Trail.
As part of this effort, the shallow water craft boarded and searched South Vietnamese fishing junks for smuggled weapons and other contraband (during USS Loyalty‘s first patrol alone, her crew boarded 348 junks, detained two and arrested 14 enemy smugglers), served as mother ships for replenishing the needs of “Swift” boats, provided gunfire support to U.S. forces ashore, (on 22 and 23 March 1966 the USS Implict alone fired nearly 700 rounds of 40mm ammunition supporting small South Vietnamese naval craft under fire from enemy shore batteries), gave special operations support to the American Advisory units and performed hydrographic surveys on shoreline depths.
After the war, it was the Aggressive-class MSOs who were tasked with Operation End Sweep–removing mines and airdropped Mark 36 Destructors laid by the U.S. in Haiphong Harbor in North Vietnam and other waterways.
In all some 10 MSO’s were part of Seventh Fleet’s Mine Countermeasures Force (Task Force 78), led by Rear Adm. Brian McCauley, during this six-month operation in the first half of 1973.
At the height of their involvement in Vietnam, the Navy started a mid-life extension and modernization process for roughly half of their MSOs. Running at $1.5 million per ship, the old Packard engines were removed and replaced with new aluminum block Waukesha diesels. The first generation mine sonar was swapped out for the new SQQ-14. As additional space on the foc’sle was needed for installation of the SQQ-14 cabling, the WWII-era 40mm Bofors bow gun was replaced with a mount for a twin 20 mm Mk 68. New sweep gear to include a pair of PAP-104 cable-guided undersea tools were added as was accommodation for clearance divers and two zodiacs powered by 40hp outboards.
Just 19 were updated to the new standard, and the MSO fleet began to severely contract.
Several took some hard knocks, especially when it came to fires.
USS Avenge (MSO-423) was gutted by a fire while drydocked at Bethlehem’s Fort McHenry Shipyard in Baltimore in 1969 and stricken the next year after a survey found her too far gone. An earlier flash fire on USS Exultant (MSO-441) while underway in 1960 claimed five lives though the ship herself was saved. USS Force (MSO-445) was not so lucky when on 24 April 1973 she lost off Guam after when a fuel leak was ignited by the No.1 Engine turbocharger and spread rapidly throughout the ship. USS Stalwart (MSO-493) capsized and sank as a result of fire at San Juan, Puerto Rico, June 25, 1966. USS Enhance (MSO-437), USS Direct (MSO-430) and USS Director (MSO-429) likewise suffered serious fires but were saved.
USS Prestige (MSO-465) ran aground and was stranded in the Naruto Straits, Inland Sea, Japan on 23 Aug 1958 and was abandoned as a total loss. Similarly, USS Sagacity (MSO-469) in March 1970, grounded at the entrance to Charleston harbor, causing extensive damage to her rudders, shafts, screws, keel, and hull, leading her to be stricken that October.
The Royal Navy diesel submarine HMS Rorqual bumped into the USS Endurance (MSO-435) while docking at River Point pier in Subic Bay, Philippines in 1969 while USS Forrestal (CVA-59) collided with the USS Pinnacle (MSO-462) at Norfolk in 1959. In all cases, the damage was slight.
USS Valor (MSO-472), just 15 years old, was found to be “beyond economical repair” in a survey in 1970 and scrapped.
By the end of Vietnam, the MSOs retained were converted to U.S. Naval Reserve Training (NRT) tasking classified as Naval Reserve Force (NRF) ships, used for training their complements of reserve crews one weekend a month two-weeks during the summer. This changed the crews from 7 officers, 70 enlisted (77 total) when on active duty, to 5 officers, 52 enlisted plus 25 reserve while a NRF vessel.
USS Energy (MSO-436) and Firm (MSO-444) were transferred to the Philippines, while USS Pivot (MSO-463), Dynamic, Persistent and Vigor went to Spain. Others, unmodernized, were sold for scrap.
By the 1980s, the European war scenario relied on North Atlantic Treaty Organization (NATO) allies to participate substantially in mine warfare operations, and U.S. mine hunters continued to decline until just the 19 modernized 1950s MSOs, built for Korea and validated in Vietnam, remained in the NRF.
During this period they often spent much time at the Mine Countermeasures Station at Panama City, Florida where they tested the first versions of the AN/WLD-1 (V) unmanned Minehunting systems, developed to scour the water for bottom and moored mines.
A few NRF MSOs were activated to assist in the Persian Gulf in 1987-88 during the tanker escort period (Operation Earnest Will) that involved Iranian sea mines, typically old Russian M08 contact types, swept.
Three sweepers: USS Fearless (MSO-442), USS Illusive (MSO-448), and USS Inflict (MSO-456), were towed 9,000 miles by the salvage ship USS Grapple (ARS-53) from Little Creek, Virginia, to the Persian Gulf.
While conducting minesweeping operations in the northern Persian Gulf, Inflict discovered and destroyed the first of 10 underwater contact mines deployed in a field across the main shipping channel.
Then came the affair with Saddam in 1990.
Four minesweepers, USS Leader (MSO-490), USS Impervious (MSO-449), USS Adroit (MSO-509) and the brand new USS Avenger (MCM-1), were loaded aboard the Dutch heavy lift ship Super Servant 3 on 19 August 1990 at Norfolk and offloaded 5 October 1990 in the middle east.
You may not remember now, but Desert Storm at sea was a mine war, with USS Tripoli and USS Princeton (CG 59) rocked by exploding mines. Saddam sewed more than a 1,000 of his deadly easter eggs across the northern Gulf and it was the job of the sweepers, along with allied boats and helicopters and some 20 different EOD clearance teams, to clear the way for a possible D-Day style amphibious invasion by the Marines as well as hacking a path through the danger zone for battleships to approach for NGFS.
And with the victory in the desert, the MSOs were paid off, replaced nominally by a new class of (since disposed of) Osprey-class MHCs and the rest of the Avengers.
Between 1989-1994 the last of the MSOs were decommissioned and stricken with the healthiest four units transferred to the Republic of China Navy (Taiwan) in 1994-95: USS Conquest (MSO-488), USS Gallant (MSO-489), USS Pledge (MSO-492), and USS Implicit (MSO-455) as ROCS Yung Tzu (MSO-1307), ROCS Yung Ku (MSO-1308), ROCS Yung Teh (MSO-1309), ROCS Yung Yang (MSO-1306), respectively, are still in service.
Six were held on red lead row until as late as 2002, when they were scrapped despite the pleas from veterans’ groups to preserve one, with the MARAD claiming it was policy not to donate wooden ships due to the cost and magnitude of the maintenance required for upkeep.
In all, some 50,000 sailors served at one time or another on these wooden ships and are very well organized in The Navy MSO Association.
Finally, the MSO sailors were came across the old USS Lucid (MSO-458) which had been sold as scrap for $40,250 back in 1976 and had been used as a houseboat ever since.
Donated, the ship has become part of the Stockton Historical Maritime Museum since 2011 and is open to the public.
She is the only MSO preserved in the West.
In Holland, HNLMS Mercuur (A856), after her decommissioning in 1987, was preserved as a museum ship, first in Amsterdam, later in Scheveningen. She will be towed to the city of Vlissingen at some point this winter, and re-open as a museum ship in Vlissingen’s Perry dock around March 2017.
In all, the class served 40 years in a myriad of tasks and a few are still around and kicking.
Not bad for some forgotten old wooden boats.