Tag Archives: Operation End Sweep

Warship Wednesday, Feb. 22, 2023: A Dozen Stars and a Wigwam

Here at LSOZI, we take off every Wednesday for a look at the old steam/diesel navies of the 1833-1954 time period and will profile a different ship each week. These ships have a life, a tale all their own, which sometimes takes them to the strangest places.- Christopher Eger

Warship Wednesday, Feb. 22, 2023: A Dozen Stars and a Wigwam

U.S. Navy Photo by JOC(AC) Warren Grass. National Archives Catalog #: 80-G-K K-98130

Above we see the unpresuming Navajo/Cherokee/Apache-class fleet tug USS Tawasa (AT-92) departing Subic Bay bound for Haiphong in February 1973 to take part in Operation End Sweep. Don’t let her workaday appearance fool you, launched eight decades ago today– 22 February 1943– she saw more hairy situations than many battleships across her 32-year career and helped boil the sea.

A new type of tug, for a new type of war

With the immense U.S. Naval build-up planned just before WWII broke out, the Navy knew they needed some legitimate ocean-going rescue tugs to be able to accompany the fleet into rough waters and overseas warzones. This led to the radically different Navajo/Cherokee class of 205-foot diesel-electric (a first for the Navy) fleet tugs.

These hardy 1,250-ton ships could pull a broken-down fleet carrier if needed (Tawasa would prove that in 1965) and had long enough sea legs (10,000 miles) due to their economical engines to be able to roam the world. Armed with a 3″/50 caliber popgun as a hood ornament, a matching pair of twin 40mm Bofors, and some 20mm Oerlikons, they could down an enemy aircraft or poke holes in a gunboat if needed.

In all, the Navy commissioned 28 of these tough cookies from 1938 onward, making a splash in Popular Mechanics at the time due to their impressive diesel-electric power plant consisting of a quartet of GM 12-278A diesels driving four GE generators and a trio of GM 3-268A auxiliary services engines, generating 3,600shp.

Their war was hard and dangerous with 3 of the ships (Nauset, Navajo, and Seminole) meeting their end in combat, and the 25 that made it through the crucible going on to serve in other conflicts, and under other flags.

The Cherokee/Navajo class would prove successful enough that 22 follow-on tugs– with the same hull form and engineering plant but with a re-trunked exhaust that shrunk the funnel diameter– of the Abnaki class would be constructed during the war, and two (Wateree, lost in a 1945 typhoon; and Sarsi, sunk by a mine off Korea in 1952) lost in Navy service. 

Meet Tawasa

The hero of our story, USS Tawasa (AT-92) was laid down on 22 June 1942 at Portland, Oregon, by the Commercial Iron Works, a small firm that would crank out no less than 188 hulls for Uncle Sam during the conflict ranging from landing craft to escort carriers. Tawasa’s launch date, some 80 years in the rearview, saw her sponsored by Mrs. Thomas F. Sullivan, the tragic gold star mom of the five lost Sullivan brothers.

The first U.S. Navy vessel named for a Florida branch of mound-building Muskhogean Indians subsequently named the Apalachicola tribe, she commissioned on 17 July 1943, just under 13 months after her first steel was cut.


Following her shakedown cruise off California, Tawasa was assigned to Service Force, Pacific Fleet, and left Pearl Harbor in early November, bound to spend Thanksgiving 1943 in the Gilbert Islands, which were being taken by Marines.

USS Tawasa (ATF-92) underway, circa 1943-1945, location unknown. David Buell for his father CWO4 Benton E. Buell USN, Ret. USS Tawasa Chief Engineer, 1962-63. Via Navsource http://www.navsource.org/archives/09/39/39092.htm

Christmas saw her in Tarawa and the New Year of 1944 with TF 52 pushing through the Marshall Islands, where she lent a hand in the landings at Kwajalein, Majuro, and Eniwetok, at times pinch-hitting as a destroyer acting as a screening vessel with her overheating and cranky WEA-2 sound equipment in the water. Her ASW armament if she had a contact? Just eight “ashcan” style depth charges on two short gravity racks over her stern.

As noted by DANFS:

Off Kwajalein Atoll on the 31st [of January], Tawasa took soundings enabling Mississippi (BB-41) to approach the shore for close bombardment. The tug then performed salvage, towing, and screening duty until 18 February when she moved to Eniwetok to assist in the assault that was to strike that atoll the next morning. She supported operations until the atoll was secured and remained in the area for almost two months, providing services to American ships using this new base.

Tawasa’s War Diary for 30/31 January 1944:

Continuing with TF52, she would soon be assisting combat-loaded LSTs landing Marines and gear on Saipan in June.

With the Marianas wrapping up, by late July Tawasa would be reassigned from TF52 back to ServRon, South Pacific, and placed on a series of unsung missions. She became particularly adept at pulling LCIs off the beach. Her embarked divers came in handy when it came to recovering lost anchors and chains, along with conducting submerged inspections of recently captured ports and leaky hulls, while her DC teams would often fan out to weld 1/4-inch steel sheeting over holes in the side of battle damaged landing craft. Her 20-ton derrick boom allowed her to salvage all manner of objects from the seafloor. Meanwhile, her sonarmen and radar operators would keep their eyes and ears peeled for interloping enemy aircraft and vessels of all types.

The Japanese surrender found our tug in Guadalcanal, where she had just transported military passengers from the Russell Islands. Post VJ-Day, she remained forward deployed except for a trip stateside to California and would operate in Chinese and Japanese waters well into 1947.

In the end, Tawasa would earn three battle stars for her WWII service.


While a wide variety of brand new ships wound up in mothballs in the days after WWII– some being towed to red lead row right from the builders’ yards– these fleet tugs remained on active service. No rest for the working man.

The Cherokee class fleet tugs listed in the 1946 Jane’s, Tawasa included. Note that the list includes the Abnaki-class half-sisters as well.

Alternating between Alaska and Guam in the late 1940s and early 1950s, Tawasa was deployed to the 7th Fleet to serve in the Korea conflict, assigned alternatively to the ports of Cho Do, Sokcho, and Chinghai while under the control of TF 92 from July 1952 through January 1953. In this, she added two further battle stars to her salad bar.

Returning stateside, she spent six months in overhaul at the San Francisco Naval Shipyard. When she emerged in November 1953, a terrific series of images were captured of her for the U.S. Navy Bureau of Ships files, detailing her radar (SO-4), radio, and overall fit. If you are a modeler looking for shots of a 1950s Cherokee class tug, the National Archives has you covered with this series:

Note that she still carries her WWII twin Bofors mounts. 19-NN-ATF 92 Tawasa-145199

19-NN-ATF 92 Tawasa-145203

19-NN-ATF 92 Tawasa-145715

19-NN-ATF 92 Tawasa-145197

19-NN-ATF 92 Tawasa-145716

19-NN-ATF 92 Tawasa-145717

19-NN-ATF 92 Tawasa-145201

19-NN-ATF 92 Tawasa-145714

Note the two bridge wing 20mm single Oerlikons. These would be replaced by M2 .50 cals by Vietnam while the Bofors would be deleted about the same time. 19-NN-ATF 92 Tawasa-145202

19-NN-ATF 92 Tawasa-145200

19-NN-ATF 92 Tawasa-145198

19-NN-ATF 92 Tawasa-145713


Fielded in 1952 without full-scale war shot tests, the 500-pound Mark 90 “Betty” nuclear depth charge was seen as an ace-in-the-hole against rapidly growing fleets of schnorkel-equipped Soviet Whiskey-class submarines, of which Moscow ordered a staggering 215 in four different versions (Projects 613, 640, 644, and 665) between 1949 and 1958.

Carrying a W7 Thor tactical fission bomb with a theoretical yield of up to 30 kilotons– twice the force of the Hiroshima bomb– it was thought that a single Betty dropped via a patrol plane would be enough to clear out a whole nest of Whiskeys.

But the Navy wanted to be sure the theory held.

Enter Operation Wigwam, a full-scale test of a live device.

Conducted in May 1955 some 500 miles southwest of San Diego in water 16,000 feet deep, Tawasa tugged a Betty as part of a six-mile long towline that included a trio of identical white-painted 4/5-scale submarine hulls (704 tons, 140 foot long with a 20-foot beam complete with correct bulkhead spacings to spec and 1-inch HST steel hull plating) dubbed “Squaws” which were filled with instruments. 

The three Squaw submarine mock-ups generally mimicked the same hull construction techniques as seen on the Navy’s SS-563 (post-war Tang) class diesel GUPPY boats, which were at least as strong if not stronger than Soviet Whiskey boats. The targets were fitted with extensive seismography instruments at 52 locations spread throughout their compartments.

With the Squaws submerged at a depth of 250-290 feet at three different distances from the device, the Betty was rigged some 2,000 feet under the keel of its support barge and the Wigwam task force beat feet to observe from five miles away.

The resulting “hot” bubble from the submerged blast grew to over 4,600 feet across when it broke the surface and rose some 1,900 feet above the water at its height.

Squaw 12, the closest to the device, simply disappeared.

Here is the view from five miles out. Hydrophones at Point Sur, Hawaii heard the “thump” of Wigwam from 2,500 miles away. NARA 374-ANT-30-30-DPY-11-20

The gist of the 56-page after-action report on the squaws:

The external pressures applied to the three SQUAW targets in Operation Wigwam were measured with pressure gages, and the deformations of the hull were measured with strain and displacement gages. The results indicate that SQUAW-12 was at a horizontal range of 5150 ft and a depth of 290 ft the peak shock pressure at the hull was about 850 psi and the target was destroyed, probably within 10 msec. SQUAW-13 was at a horizontal range of 7200 ft and a depth of 260 ft the peak dynamic pressure at the hull was about 615 psi, and the hull was probably near collapse but did not rupture. The estimation is that the lethal horizontal range of the SQUAW target under the Wigwam test conditions is about 7000 ft for a depth of 250 ft and about 4500 ft for a depth of 70 ft.

Even though at least 362 personnel of the task force’s 6,732 men embarked– clad just in working gear with no flash or NBC protection– would have mildly dirty dosimeters after the event, and contaminated water was found at several depths during the weeks following the test, it was judged that Betty was safe-ish enough to be used under certain conditions, and was more than capable of sinking an enemy sub (or three) within a two-mile radius of its impact if used correctly.

This 11-minute film covers the test in great detail, including Tawasa and her six-mile squaw-laden towline.

Betty would remain in service until 1960 when it was replaced by the multipurpose B57 nuclear bomb during the mid-1960s. In its depth charge variant, the hydrostatic fuzed B57 had a selectable yield up to 10 kt– only about one-third of the Wigwam device– and could be dropped by P-3s, S-3s, and SH-3s as well as the short-lived Drone Anti-Submarine Helicopter (DASH). It was thought that in most scenarios, the B57 depth charge would only be dialed in at 5 kt. It would finally be withdrawn in 1993.

Anyway, back to our ship.


Dusting off and cleaning up post-Wigwam, Tawasa would continue to serve with the 7th Fleet on WestPac deployments, including four to Vietnam (May-Oct 1968, April-Sept 1969, May-Sept 1970, and Feb-June 1972). For this, she would earn seven Vietnam-era campaign stars.

Her most notable moments during this era included the largest operational tow made by a solo tug of the Pacific Fleet: 33,946 tons, when she pulled the decommissioned USS Bunker Hill (AVT-9) from San Francisco to San Diego, and coming to the rescue of the shattered destroyer USS Frank E. Evans (DD-754) which had been sheered in two by the Australian aircraft carrier Melbourne during Southeast Asian Treaty Organization exercises in the South China Sea.

Tawasa took the remaining stern section in tow and returned it to Subic Bay.

2 June 1969 SH-3 helicopters from USS Kearsarge (CVS-33) join search and rescue operations over the stern section of USS Frank E. Evans, as USS Everett F. Larson (DD-830) stands ready to offer assistance (at right). NH 98649

She closed out her Vietnam service with Operation End Sweep off Haiphong in 1973. During the six months of End Sweep, 10 ocean minesweepers, 9 amphibious ships, 6 fleet tugs, 3 salvage ships, and 19 destroyer types operated in RADM Brian McCauley’s Task Force 78, sweeping hundreds of the aircraft-laid mines.

By 1973, she was one of 25 of her class still in Navy service but her days were numbered.

Jane’s 1973-74 listing, in which the class is dubbed the Apache class. Note that the list includes the Abnaki-class half-sisters as well.


With a final scoresheet that would include three battle stars for World War II service, two for Korea, and seven for Vietnam, Tawasa was decommissioned and struck from the Navy list on April Fool’s Day 1975. She was sold for scrapping the following August.

There has not been a second Tawasa on the Navy List.

Much of her logs and photos are in the National Archives.

As for the rest of her sisters, many continued in U.S. Navy service until as late as the 1970s when they were either sunk as targets or scrapped. A number went as military aid to overseas allies in Mexico, Colombia, the Dominican Republic, Indonesia, and elsewhere. One sister, USS Apache (ATF-67) who served as the support tender for the bathysphere Trieste, was transferred in 1974 to Taiwan and continues to serve as ROCS Ta Wan (ATF-551). Added to this is USS Pinto (AT-90), which has been in Peru as BAP Guardian Rios (ARB-123), and USS Sioux (AT-75), which lingers as the Turkish Navy’s Gazal (A-587).

The final Abnaki-class half-sister in the Navy’s inventory, ex-USS Paiute (ATF-159), was stricken in 1995 after 44 years of service spanning WWII, Korea, Vietnam, and the First Gulf War, then scrapped in October 2003 at Portsmouth.

The legacy of U.S. Navy fleet tugs is kept alive by NAFTS, the National Association of Fleet Tug Sailors. The only Navy tug museum ship is the former ATA-170-class auxiliary tug USS Wampanoag/USCG Comanche, which will be opened to the public in the coming months.

When it comes to Betty, the National Museum of the U.S. Navy has an inert casing on display, noting, “After tests at sea and in the Nevada desert, the Navy soon determined that the Mk 90 was not a practical weapon and retired the system in 1959.”

Ships are more than steel
and wood
And heart of burning coal,
For those who sail upon
them know
That some ships have a

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ROK Navy strikes last former USN ship

USS Beaufort (ATS-2) underway off Hawaii, circa 1984-88. Brian O'Connor, MM1 (SW/DV) USN Ret, via Navsource

USS Beaufort (ATS-2) underway off Hawaii, circa 1984-88. Brian O’Connor, MM1 (SW/DV) USN Ret, via Navsource

When the Republic of Korea Navy (ROKN), founded as the Korean Coast Guard 11 Nov 1945 with some captured Japanese coastal vessels, stood up in 1949, their first modern acquisition was a 600-ton submarine chaser, the former USS PC-823, which was bought with money raised by subscription and dubbed ROKS Baekdusan (PC 701).

Throughout the next several generations, the primary source of warships for the ROKN was the U.S. Navy with a host of surplus Fletcher, Sumner and Gearing-class destroyers and WWII-era amphibs and submarines.

In the late 1970’s, Park Chung-hee made it a point to start building indigenous vessels and the first major all-South Korean-made naval vessel, the frigate ROKS Ulsan (FF 951), was commissioned in 1980.

Now the fleet is all-ROK with the retirement of the last former U.S. Navy ship.

ROKN ship Pyeongtaek (ATS-27), formerly the USS Beaufort (ATS-2), an Edenton-class salvage and rescue ship, was decommissioned 28 Dec. 2016 after 44 years of combined service between the two allies.

Built at Brooke Marine, Oulton Broad, Lowestoft, United Kingdom, the 3,100-ton salvage ship was commissioned 22 January 1972 in the U.S. Navy and spent her entire career in the Pacific, notably participating as a support ship for the minesweepers engaged in Operation End Sweep, the removal of mines from Haiphong harbor in North Vietnam.

Decommissioned on 8 March 1996 and struck from the Navy List, she was disposed of through the Security Assistance Program, transfer and cash sale of the hull to the Republic of Korea Navy who recommissioned her ROKS Peyongtaek on 1 April 1997.

Now she will become razor blades.

Interestingly, Beaufort/Peyongtaek‘s class leader USS Edenton (ATS-1), struck from the Navy List 29 December 1997 after 26 years active duty, was turned over to the U.S. Coast Guard 10 July 1999 and, recommissioned as the medium endurance cutter USCGC Alex Haley (WMEC-39), is “The Bulldog of the Bering” based out of Kodiak, Alaska.

She is not expected to decommission for another decade or so.


Maybe the South Koreans will let the USCG go over Peyongtaek for spare parts before they send her to the breakers.

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.

UQS-1 mine-locating sonar panel currently at the Museum of Man in the Sea in Panama City. Photo by Chris Eger

UQS-1 mine-locating sonar panel currently at the Museum of Man in the Sea in Panama City. Photo by Chris Eger

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.

USS Lucid as commissioned, she is the only MSO afloat in the Western hemisphere

USS Lucid as commissioned, she is the only MSO still afloat in the Western hemisphere. Note her 40mm gun.

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.

USS LEADER (MSO-490) Caption: Is seen from a Saigon based SP-2H Neptune aircraft while on a Market Time patrol during the later 1960s. The plane and ship are exchanging information on coastal traffic in the area. Description: Catalog #: NH 92011

USS LEADER (MSO-490) Caption: Is seen from a Saigon based SP-2H Neptune aircraft while on a Market Time patrol during the later 1960s. The plane and ship are exchanging information on coastal traffic in the area. Description: Catalog #: NH 92011

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.

End Sweep's line in action

End Sweep’s line in action

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.

A bow view of the ocean minesweeper USS FORTIFY (MSO 446) underway, 6/8/1982

A bow view of the ocean minesweeper USS FORTIFY (MSO 446) underway, 6/8/1982. National Archives Photo.

A starboard view of the ocean minesweeper USS ILLUSIVE (MSO 448) underway, 8/13/1984

A starboard view of the ocean minesweeper USS ILLUSIVE (MSO 448) underway, 8/13/1984. National Archives Photo.

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.

wld-1-2 wld-1-mms

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.

Crewmen handle a minesweeping float on the stern of the ocean minesweeper USS INFLICIT (MSO 456), 4/27/1988

Crewmen handle a minesweeping float on the stern of the ocean minesweeper USS INFLICIT (MSO 456), 4/27/1988. National Archives Photo

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.

Impervious, foreground, and Adroit (MSO 509) sit aboard the Dutch heavy lift ship Super Servant 4 as its deck is submerged to permit minesweepers to be unloaded. Photo by PHAN Christopher L. Ryan

Impervious, foreground, and Adroit (MSO 509) sit aboard the Dutch heavy lift ship Super Servant 4 as its deck is submerged to permit minesweepers to be unloaded. Photo by PHAN Christopher L. Ryan

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.

The ocean minesweeper USS INFLICIT (MSO 456) heads towards the Persian Gulf to support US Navy escort operations, 9/1/1987

The ocean minesweeper USS INFLICIT (MSO 456) heads towards the Persian Gulf to support US Navy escort operations, 9/1/1987