sunset of naval netlaying after WWII

Some changes to the US Navy after WWII were both readily apparent and abrupt. The carrier-based warplane replaced battleship gunnery as the most potent offense at sea. Smokescreen-laying, an important art for destroyer captains in 1939, was more or less moot ten years later due to the near-universal fitting of radar on warships. And so on.

The decline of naval defensive nets after WWII was neither fast, nor with a simple explanation. In the US Navy the discipline sort of just quietly went away, slowly, over a period of about 15 – 20 years…yet, the decline was unmistakable even as soon as WWII’s end in 1945.

Little is said as to how or why naval nets vanished, or what happened to the US Navy’s many net warfare ships after WWII. So perhaps this will be of value.

(USS Pinon (AN-66) hauls in a German anti-submarine net at Cherbourg, France following the city’s liberation during WWII.)

(An inert Polaris ballistic missile being launched in 1963 from a buoyant test cylinder tended by USS Butternut (AN-9), a WWII veteran net ship.)

(The Dominican Republic navy’s Separación, which had been USS Passaconaway (AN-86) during WWII, during the 1990s.)

nets during WWII

Naval nets originated during the Spanish-American War era, and the Royal Navy used net barriers during WWI. They were further developed inbetween the world wars. In the US Navy there were three types of naval nets in use during WWII.

Type S

Type S was designed to prevent enemy submarines from entering harbor mouths or natural choke points in the sea. These were the biggest of the three types.

The support was the jackstay. It was a 1 5/8″ steel cable of six braided strands with 19 individual wires in each strand. It was heavy, weighing 4¼ lbs for each linear foot; and also very strong as it supported the weight of the net. Jackstays were up to 290′ long and had open sockets at each end.

The vertical and bottom sides of the net were the perimeter, which was a 1″ steel cable.

The net itself was 1″ rope, a braid of 70 galvanized steel and 21 hemp fiber threads. Before WWII the US Navy experimented extensively and found that this was ideal; giving the best combination of strength and flexibility. The hemp threads were soaked in a rust inhibitor before assembly; the idea being that under tension they would ooze it out onto the steel threads. It was delivered on 3,000′ reels.

To assemble a Type S Net, the jackstay and side and bottom of the perimeters were laid out. The first weave was clipped to the perimeter. Next, the 1″ rope was woven on 45° angles, alternating even/odd to over/underneath, forming 8’² ◊ shapes. These were joined by 4-way clamps. When attached to the jackstay, the finished product was a 300′ long panel, its height varying with the water depth. Successive panels were strung together as needed.

The jackstay was floated by 4’10” spheres which generated 3,092 lbs of buoyancy each. The ends had a huge 10′ x 13′ peg buoy on the seaward side and four Mk4 mooring buoys, which were 8′ x 14’8″ barrels. These were attached with 1½” iron chain to anchors; either old ship anchors or 3-ton blocks of concrete.

The diagram above shows how the whole system would, in theory, stop a submarine.

Building a Type S net during WWII was an intensive task. At a minimum it was required to have a concrete pad 350′ x 150′ with pre-drilled holes to receive special pins that held the 1″ rope while the net was being woven.

This was only sufficient for one panel. Typically on large naval bases two or three pads were available, taking up a lot of space.

As nets entered service during WWI, a counter was developed, the net cutter. These were angled banks of hardened, sharpened steel dogteeth.

During WWII these sometimes did work, often did not, and were a hassle the rest of the time. By mid-1942 German u-boat commanders were requesting they be omitted and this was done. Other navies similarly abandoned them. Net cutters were extinct on new submarines after WWII.

Type I

Similar to the Type S, the Type I (or “indicator”) net differed in that it was intended to not stop a submarine. Here, the net was attached to the jackstay not by clamps but by burster clevises. These were like turnbuckles which snapped when a predetermined stress was put on them.

Now freed from the jackstay, the net was hoped to snarl onto the diving planes, deck gun, etc of the submarine. The net remained attached to two Mk2 floats, which had a reel for 300′ of tow line. When a submarine snarled the net, the line played out (preventing the Mk2 from being dragged underwater) and activated a chemical smoke pot. With this, not only was the threat detected but patrol craft could follow it.

Type T

This was an entirely different style than the other two, and was to protect against torpedoes fired by intruding submarines or attacking naval torpedo planes.

This objective had to counteract kinetic energy. A submarine contacting a net would be coming at very slow speed (many WWII submarines had submerged speeds in the single digits) with the jolt spread out over the area of the whole bow. On the other hand a torpedo would be coming in much faster and with all its kinetic energy received in twelve square inches.

The Type T was made of 16″-diameter grommets. These were ¼” steel wire braided seven times and then woven into a hoop. This diameter was chosen as WWII torpedoes were 17¾” to 24″ diameter.

These were woven, as described below, into 72′ panels, then attached to a headrope. Unlike the submarine nets, there were no jackstay with clips, as it was found that these themselves could fail from the jolt of a torpedo. The headrope attached to buoys. On the bottom, 3-ton concrete blocks or old ship anchors were used; sometimes both.

Type T nets were very heavy. One individual 72′ panel (not including buoys or anchors) weighed 4¾ tons and took up a 13’4″ x 2’6″ x 4′ space on a cargo ship. They were handled in bundles as seen below.

If the S and I types were hard to manufacture, the Type T was an order of magnitude worse. Each individual grommet had to be hand-wound into a hoop at the same time it was interleaved into the ones next to it. During WWII the United States tried and failed to find a way to automate the process. The work itself was not easy, as the wire was under tension any slip-up could result in injury. A two-person team could make between 12 – 20 per hour; keeping in mind that just one panel had over a thousand.

A proposed simpler replacement, a slinky-type drop-down coil, failed its tests and the Type T remained in use throughout WWII and beyond.

(An exercise torpedo being stopped by a Type T net.) (official US Navy photo)

comparison with other WWII navies

The major warring powers of WWII all used nets, both anti-submarine and anti-torpedo, to one degree or another. The items – nets and ships – were generally similar to the US Navy’s concepts. The major allies also received some American nets via Lend-Lease.

(The German netlayer Netzleger IV was a converted merchant ship. German anti-submarine nets were similar to the American Type S, but used a square-pattern weave of 3’3″ squares and a less elaborate rope type. German anti-torpedo nets were similar to the American and British grommet types. Netzleger IV survived WWII and was taken by Belgium as reparations. Converted back to a merchant, it sailed as M/V Sofia T until sinking in a 1961 storm.)

(The Royal Navy’s A/T Net was extremely similar to the US Navy’s Type T; not surprising as the American design largely copied the British.)

Tiburon Net Depot

The US Navy had net depots before entering WWII and built a large number of new ones during the war. Of these, arguably the most famous was at Tiburon, CA.

Originally a coaling station, Tiburon was made redundant when the fleet switched from coal to fuel oil in the early 20th century. In 1940, Tiburon was reacquired by the US Navy and converted into a net depot. The gigantic traveling coaling crane was ideal for moving heavy loads of netting onto transport ships, or into the water for training.

During WWII Tiburon was, along with Indian Island, WA, one of the biggest Pacific fleet net depots and one of a handful that could do everything: assembly, testing, shipping, training, and so on.

After WWII Tiburon remained in reduced-capacity use. It was again fully reactivated for the Korean War in 1950. As net use declined in the late 1950s, Tiburon became not only the main net depot for the Pacific fleet, but also the main training site and eventually, the last dedicated net training site for the whole US Navy. In 1958, the base was closed and in 1964 was disposed of by the Department of Defense.

The crane was torn down in 1981. As of 2021, a number of WWII-era buildings still remain on the site, which is now split between parks and civilian oceanography.

net tenders

These were warships specifically intended to tend naval nets. The US Navy operated three classes during WWII. After WWII these would end up being the last of their kind.

the Aloe class

A prewar design, this was the class in progress when the USA entered WWII in December 1941.

The Aloe class displaced 805t full and measured 163’2″ x 30’6″ x 11’8″. It was powered by a single diesel engine (the type could vary) turning one propeller shaft, for a maximum speed of just 12½ kts. The intended crew size was 4 officers and 44 enlisted sailors.

(USS Sandalwood (AN-32) servicing a net off North Carolina during WWII. It has pushed aside a broken area of net and is preparing to graft in a replacement section. This ship served the French navy after WWII.)

As designed, the Aloe class was armed with a Mk10 or Mk22 open-mount 3″ gun forward,  two M2 Browning .50cal machine guns, and a single Mk1 Y-Gun, which simultaneously fired a depth charge to both sides (the Aloe class was designed without sonar, however). During WWII this was changed, first the two .50cals were upgraded to 20mm AA guns, and then an additional one or even two more 20mm guns at the expense of the basically useless Y-Gun. Several even received a twin 40mm as the kamikaze threat increased.

A total of 32 Aloe class ships were built. The leadship USS Aloe (AN-6) commissioned on 11 June 1941 and the last, USS Yew (AN-37) on 1 July 1942.

The most prominent feature of the Aloe class (and all WWII American net tenders) was the huge horns-type device over a flattened, curved upper bow to handle nets. There was also a 12-ton boom crane.

During WWII, no Aloe class ship was sunk. However USS Mahogony (AN-23) was so heavily damaged by typhoon “Ida” several days after WWII ended that the US Navy wrote it off.

the Ailanthus class

This was a supplemental design of mid-1941, when it appeared increasingly likely the USA might be pulled into WWII. It was intended to be lower-cost, and also to use a lot of wood as the USA feared steel shortages should the country go to war. As intended, 30 were ordered with 20 allocated to Lend-Lease, and the remaining 10 to the US Navy.

This contract was cancelled before work started and was replaced by a contract for 20 ships, with options (both later taken up) on an additional 14 and 6 hulls. As the USA was now in WWII, priority went to the US Navy and only five went to the British.

(USS Satinleaf (AN-43) during WWII. A veteran of the Leyte Gulf battle, it decommissioned only seven months after WWII.)

The Ailanthus class displaced 1,118t full and measured 198′ x 37′ x 13′. It had a diesel-electric lineup; the single engine was not linked to the propeller shaft but rather to a generator which in turn was wired to an electric motor that turned the propeller. This was chosen as the United States feared a production bottleneck of reduction gearboxes. The top speed was 12 kts and the complement was 56.

Like the Aloe class, the Ailanthus class carried a 3″ gun forward. The original AA armament was two single 20mm guns. A few later received an additional pair of 20mm guns on the deckhouse.

During WWII the USA was never short of steel and the decision to use wood was regretted. Of the 40 ordered, 5 went to Lend-Lease and of the other 35, only 30 were commissioned. The 29th, 30th, and 38th through 40th hulls were completed as plain tugboats in 1944.

The leadship USS Ailanthus (AN-38) commissioned 2 December 1943 and the last, USS Stagbush (AN-69) on 30 August 1944.

USS Ailanthus (AN-38) ran aground and was destroyed in February 1944. USS Viburnum (AN-57) hit a Japanese mine in 1944 and was never fully repaired. The rest survived WWII.

the Cohoes class

These were the final US Navy net tenders of WWII and as it turned out, ever. Work did not begin until the late autumn of 1944. They were split between four shipyards, with three of the four being inland on the Great Lakes.

The Cohoes class displaced 775t full, and measured 168’6″ x 33’10” x 10’10”. The maximum speed was 12¼ kts and the complement was 4 officers and 42 enlisted sailors.

(USS Cohoes (AN-78) running builder’s trials during WWII. This ship still had the remainder of WWII ahead of it, and decades later the Vietnam War. This photo shows the class’s defining feature; moving the 3″ gun aft to free up more net handling space forward.)

The armament was one 3″ gun and three 20mm AA guns, one in an aloft pedestal. The 3″ gun was sited aft, giving more net-handling area forward than the Aloe class.

The leadship USS Cohoes (AN-78) commissioned on 23 March 1945 and the final ship, USS Yazoo (AN-92) on 31 May 1945. The short span was because the four shipyards were mass-producing the class all at the same time.

None were lost during WWII.

cancelled ideas

Just prior to the attack on Pearl Harbor in 1941, the US Navy planned three very large (4,626t, 458′-long) “super net tenders”, the Osage class. The leadship USS Osage (AN-3) was laid down on 1 June 1942, but with the USA now in WWII it was decided to convert all three to amphibious assault ships while still under construction.

(USS Osage (LSV-3) retained the blunt bow which would have handled nets in the original role. USS Osage decommissioned into mothballs two years after WWII. In 1955, it was planned to reporpose USS Osage as a mine countermeasures mothership but Congress never funded this. This ship was never reactivated and was scrapped in 1975.) (photo via navsource website)

net transporters and gate vessels

Nets and their buoys were heavy and bulky. Type Ts were especially problematic as they were delivered pre-assembled. During WWII the US Navy moved them by cargo ships or (less ideally) fleet stores ships, which were urgently needed for other tasks. There were however a few specialist ships to transport nets.

Four Indus class net transporters were converted from Liberty Ship freighter hulls. These had cargo holds optimized for nets and many booms to handle them. They also carried small workboats and a Sea Mule, a special boat to move nets around in the water.

(USS Sagittarius (AKN-2) during the 1945 invasion of Okinawa, with the Sea Mule circled.) (US National Archives photo)

There was another one-off type, USS Keokuk (AKN-4). During the summer of 1941, with another world war possibly looming, the US Navy made COTS (Commercial Off-The-Shelf) ship buys to quickly beef up the fleet. A 26-year old merchant freighter, the S.S. Columbia Heights, was bought for conversion into a minelayer. The 6.150t, 353′-long ship was by no means ideal, with old reciprocating steam engines and poor handling.

The US Navy had second thoughts and cancelled the minelayer conversion in May 1942. Only minor changes would be needed to adapt it to transporting nets. As such, USS Keokuk commissioned as AKN-4 instead of CM-8 on 18 May 1942.

(USS Keokuk (AKN-4) during WWII.) (photo via navsource website)

The final “piece of the puzzle” were gates. A net barrier needed a way for friendly vessels to pass. These gate nets had to perform as well as normal parts of the system, but also be moveable. It typically took between 20 mins to half an hour to move a gate one way. There were two types: a horizontal gate could be swung like a door to allow surface warships or submarines through, while a dipping gate could be lowered to allow shallower-draught warships to pass over it. Either way, there had to be a ship to do this.

Gate vessels were originally anything, usually oddball tugboats.

(USS Noka (YN-54) was a civilian tugboat acquired in 1941 via COTS buy for the US Navy’s Yard & District Craft program. It was 74′ long and powered by an Atlas Imperial diesel engine.)

Gate vessels rarely needed to move, other than when the gate was being used. Therefore a ship with an engine, navigation system, etc was wasteful so the United States used 43 non-self-propelled gate vessels, with the hull symbol YNg (the g being lowercase). These were basically just elaborate barges optimized for handling gates. Six were converted from barges of other types, three were converted surface warships, and the other thirty-four were built-for-the-purpose.

Most were not named. They had 18-man crews and carried 20mm AA guns and a searchlight for self-defense. When they needed to move, a tugboat came alongside; the advantage being that the rest of the time the tugboat could be doing something else.

(An interesting one was USS Dreadnaught (YNg-21); spelled differently and a bit more modest than the Royal Navy’s HMS Dreadnought. This had been a WWI tugboat, converted into a WWII gate vessel.)

(The nameless YNg-18, one of the built-for-the-purpose gate vessels, before the AA guns were installed.)

As WWII went on, some of the built-for-the-purpose YNg craft became surprisingly elaborate. For example YNg-39, which served the gate leading into New York City harbor, was additionally fitted with sonar and a waterproof telephone cable to Ft. Wadsworth in Staten Island.

AFTER WWII

WWII ended on 2 September 1945. With the Cohoes class finished, no future types were envisioned. The first peacetime fleet planning (which was actually done while WWII was still underway) showed an unwanted surplus of net tenders; due to lower than expected wartime losses.

the Aloe class

Of the 32 Aloe class ships, none had been sunk during WWII but as mentioned earlier USS Mahogany was lost soon after Japan’s surrender. Of the others, 3 had already been transferred via Lend-Lease leaving 28 in the US Navy on V-J Day.

Of these 28, 24 were earmarked for the mothball fleet. The first to leave service were USS Eucalyptus (AN-16) and USS Chinquapin (AN-17) which decommissioned into reserve together on 6 March 1946, six months after WWII ended. The last of this batch was USS Buckthorn (AN-14) which decommissioned on 20 August 1947.

The four earmarked for active-duty retention were USS Butternut (AN-9), USS Elder (AN-20), USS Mulberry (AN-27), and USS Hazel (AN-29).

USS Hazel, USS Mulberry, and USS Elder had relatively quiet post-WWII careers. They served in Cold War-era HDUs (Harbor Defense Units) at home and occasionally deployed abroad. They decommissioned between 1958 – 1960.

USS Butternut (AN-9)

Of this class and all the net tenders in general, USS Butternut had the most unusual career during the Cold War. When WWII ended, USS Butternut was operating in the Philippines. Unlike the bulk of the US Navy which returned home, USS Butternut remained in the area, as there were many tasks the ship was useful for: both net-related, and otherwise.

From 1947 – 1950, USS Butternut was based at Guam and serviced the declining numbers of nets at US Navy facilities in the Pacific islands. From 1950 – 1951 the ship served in Japan, and then transferred to the west coast of the USA to serve at the Tiburon facility.

With net use continuing to decline, USS Butternut was reassigned to the Polaris project in 1957. The ship was seconded to the China Lake weapons development facility for use in this effort; a massive undertaking to design the world’s first solid-fueled, submarine-fired, intercontinental nuclear missile.

Originally known as “AX”, prototype missiles could be test-fired from ashore launch pads but there naturally was no way to test the systems needed to eject a ballistic missile from underwater, without actually doing that.

USS Butternut operated from the San Clemente Island test site, a subfacility of Naval Base Coronado near Los Angeles. The ship transported the buoys, anchors, cables, and other kit needed to simulate the underwater ejection and broach sequences of a submarine launch, including the submerged cylinder and actual missile shapes themselves.

As net tenders were at their core essentially highly-specialized tugboats, USS Butternut was also useful for towing the barges and derricks needed for the Polaris tests without needing an additional tugboat.

In December 1959 the UGM-27 Polaris became an operational weapons system. USS Butternut continued in use for further refinement of the missile. With Polaris mature in 1964, China Lake wrapped up the effort and released USS Butternut.

This WWII ship still had further unique roles to play. A triple torpedo tube was installed on the superstructure for the then-new Mk46 anti-submarine torpedo. This weapon had started development in 1960. USS Butternut was ideal for the tests as the ship was mechanically reliable and relatively inexpensive to operate.

The torpedo trials lasted until mid-1969 when the triple tubes were removed. Now almost a quarter-century after WWII, the US Navy decommissioned USS Butternut on 18 July 1969. However the ship still had some more service to give. The now-nameless hull was renumbered YAG-60, an uncommissioned service craft, and assigned as a general-purpose asset to the Barking Sands Missile Range in Hawaii. In this role the hull served on another two years. After this, YAG-60 was used as a trainer. The worn-out hull was finally sunk as a weapons target in June 1977. USS Butternut served 35 years in six different roles; not a bad return on the WWII investment.

the Aloe class abroad

France: France received USS Hackberry (AN-25), USS Pepperwood (AN-36), and USS Yew (AN-37) as Lend-Lease while WWII was still ongoing. These three had been in the Mediterranean already and were transferred there to jump-start the Free French navy after the landings in southern France.

(Tarantule, the former USS Pepperwood, during the 1950s Indochina war. The French used this ship for a number of roles including patrol along the Vietnamese coast. At this time the ship was still in WWII American configuration.) (photo via Andre Pilon)

USS Locust (AN-22) was transferred shortly after WWII and renamed, appropriately, Locuste. During the late 1960s USS Rosewood (AN-31) and USS Sandalwood (AN-32) were reactivated from mothballs and transferred to France. With these, France now had six Aloe class ships in service.

(Libellule, the former USS Rosewood, in the Cold War-era French navy handling a mooring buoy. By this time the WWII American guns had been removed and new French radar and electronics installed.) (photo via navsource website)

Three of the six were assigned to France’s nuclear weapons test site at Murorua Atoll in the south Pacific.

(Tarantule, the former USS Pepperwood, serving as a buoy tender at the French Pacific nuclear test site.)

(A French nuclear weapon test at Murorua. Typically these were loose warheads suspended from a balloon; but some were either ashore on the atoll, or on a buoy in the atoll’s lagoon, or on the seabed under the lagoon. A few were full ordnance (warhead + delivery system) shots. In any of these the WWII net tenders served the scientific monitoring equipment, and sometimes the nuclear warhead itself.)

These useful ships began to leave French service in the 1970s, either being scrapped or expended as gunnery targets.

Locuste, the former USS Locust, and Scorpion, the former USS Yew, had a bizarre ending. Two of the three assigned to the Pacific nuclear site, they were not considered radioactive but given their post-WWII history there was difficulty in finding a willing scrapper. A Malaysian metal company eventually bought them. The company planned to have Locuste tow Scorpion to the scrapyard where both would be cut up. On 30 July 1978, Locuste struck a reef near Fiji and sank, taking Scorpion down with it.

L’Araignée, the former USS Hackberry, was the last to leave French service in 1977 and was scrapped in 1985.

Turkey: USS Larch (AN-21) was transferred via the Military Assistance Program in 1948. Renamed TCG AG-4, this ship was refit with a modern French radar but retained its WWII American weaponry. It curiously had a pennant number in the Turkish patrol craft sequence. TCG AG-4 performed salvage and towing missions besides net tending, and served on into the late 1990s.

Ecuador: USS Mulberry (AN-27), which had been one of the four retained on US Navy active duty after V-J Day, decommissioned in 1960 and was transferred to Ecuador in 1965 via loan. Renamed BAE Orion, the ship was used as a buoy tender, survey ship, and tugboat. BAE Orion was scrapped in 1980.

(This 1970s report to Congress shows how the USA kept track of ships transferred abroad. “LMAP” indicates USS Mulberry is on loan, beginning “11 65” or November 1965, and that it is “H71” or reported as still in-service in 1971. ILP was one of the myriad American military aid efforts during the Cold War. These were almost all WWII-era ships, and all of low-combat types: the misspelled USS ‘Mubberry’, transports, tugboats, Coast Guard boats, a barge, a water tanker, and so on.)

the Ailanthus class

With the US Navy regretting the decision to make these partially of wood, they had no future after WWII. USS Snowbell (AN-52) was destroyed by typhoon “Louise” on 9 October 1945, five weeks after WWII ended.

The others began to quickly decommission: USS Bitterbush (AN-39) only 18 weeks after Japan’s surrender, through USS Silverbell (AN-51) in January 1947. The Lend-Leased British ships were unwanted by the Royal Navy and returned to the United States for disposal after WWII.

The only one retained on active duty was USS Whitewood (AN-63). The net features were removed and USS Whitewood was reclassified as a general auxiliary (AG-129) to support arctic operations.

(USS Whitewood (AG-129) in the ice during the late 1940s.)

USS Whitewood was of limited success in the new role and was discarded in mid-1949.

One ship of this class was transferred to France, where it had an unremarkable career. Six were sold to the Republic Of China Customs service, to stem the rampant post-WWII smuggling around Shanghai. Presumably they were lost when the nationalists lost the civil war and fled the mainland in 1949.

In 1947 it was decided that not only was the Ailanthus class not wanted on active duty, it was not even wanted in the mothball fleet. The US Navy transferred the decommissioned ships to the US Maritime Administration for disposal.

Only one had an interesting life after WWII. USS Seagrape (AN-77) had been Lend-Leased as HMS Preventer and then returned after WWII. As part of the mass 1947 disposal, it was disarmed and sold to the Falkland Islands Dependencies Survey, with the net features removed. Renamed John Biscoe, it was manned by a civilian crew and mapped the seas around the Falklands. In August 1956, it was resold to the Royal New Zealand Navy and recommissioned as HMNZS Endeavour.

(HMNZS Endeavour, the former USS Seagrape / HMS Preventer of WWII.)

New Zealand used HMNZS Endeavour to support research around Antarctica. The bow horns were not reinstalled. In 1962 the RNZN sold the ship yet again, now to a Canadian fur company for use as a seal hunter. Renamed S.S. Arctic Endeavour, it was lost in a storm in 1982.

the Cohoes class

The last American net tenders, only two, USS Waxsaw (AN-91) and USS Yazoo (AN-92) were retained on active duty past 1947. The logic here was that these were fresh, new ships with minimal alterations during WWII, and as such they made ideal candidates for the mothballing program.

Of the thirteen mothballed after WWII, seven were indeed reactivated during the Cold War, having been well-preserved.

(After WWII USS Etlah (AN-79) serviced the target ships for the 1946 “Crossroads” nuclear tests at Bikini atoll and then decommissioned in 1947. It was recommissioned for Korean War service in August 1951. The WWII net gear and guns were retained, but the radar was upgraded to AN/SPS-5 as seen and new radios were added. USS Etlah continued in active duty US Navy service until 1960.) (photo via US Navy Memorial)

(USS Suncook (AN-80) decommissioned into mothballs in 1947. In 1962, the ship was reactivated, demilitarized, and transferred from the US Navy to the US Department Of The Interior. Renamed R/V Grass Valley, the former WWII netlayer served the Bureau Of Mines as a geology ship until 1968.) (photo via navsource website)

(USS Nahant (AN-83) was another Korean War recommissioning retained on active duty afterwards. This 1967 photo shows how WWII netlayers could be a challenge in rough seas, with their squat hullform and bow horns. Here the entire foredeck is awash. USS Nahant would transfer to Uruguay the next year.)

(USS Naubuc (AN-84) decommissioned one year after WWII. In 1967, the ship was “de-named” and rebuilt into the nameless YRST-4. Now displacing 873t, the essentially unrecognizable conversion was powered by four vertical cycloidial propulsors which made it slow but gave it pinpoint precision in movement. A huge cable drum forward streamed out the length of the ship and over the stern. Controlled by the Naval Underwater Warfare Center, YRST-4 supported experiments with fixed underwater acoustic arrays until 1975.)

Other than USS Cohoes described below, the last Cohoes class netlayer in the US Navy was USS Nahant (AN-83) which decommissioned on 30 September 1968. 

USS Cohoes in the Vietnam War

The class leadship USS Cohoes (AN-78) had ended WWII recovering Imperial Japanese Navy mooring buoys in the Marshall and Caroline Islands. After WWII USS Cohoes operated out of the Tiburon depot, until being decommissioned in 1947.

(USS Cohoes in 1946, still in the final WWII configuration.)

Well preserved in the reserve fleet, USS Cohoes was selected for reactivation in 1968 to support the Vietnam War. The US Navy was not interested in having a net tender in-country, but urgently needed to increase the number of salvage ships in South Vietnam. Since the WWII netlayers already had a number of salvage ship-like features, modifying USS Cohoes was the fastest and cheapest option.

The ship was extensively modernized. While the bow horns were retained, some of the other net-related features were deleted. The hull code was changed from AN to ANL.

The radio shack of USS Cohoes was gutted with the bulky vacuum tube radios of WWII removed. In their place was a AN/URC-58 for ship-to-ship communications, and a AN/URR-35 which allowed receive-only long-range transmissions.

Of the WWII radios a AN/TCS-12 was retained; this had been installed during WWII on PT boats and various types of minor / service ships; the latter of which were still now in use with the South Vietnamese navy. Finally a US Army AN/VRC-46 was installed aboard which allowed USS Cohoes to directly talk to troops ashore when close to the coastline. It used a livewire-type antenna.

The AN/UPX-12 IFF (identification friend/foe) transponder was installed so modern warships and aircraft would recognize USS Cohoes as friendly beyond visual range. The AN/UPN-12 long-range radio-navigation system was installed.

The WWII radar was removed and replaced by a civilian Decca D202. The US Navy felt that it offered better short-range resolution than seagoing military radars. A bottom profiler was installed, this was a short-range, high-frequency active sonar that provided an overview of the seafloor.

The 3″ gun was removed and machine guns were installed in the two remaining former AA platforms of WWII. Over the bridge area, an o.d. green canvas awning with a US Army-style white star was installed. The WWII lifeboats were replaced by newer and larger types. The ship’s scuba air charging station was enhanced, and a diver’s decompression chamber was installed. Storage for exotic-gas underwater welding systems were added.

A transverse (port-to-starboard) tunnel thruster was installed in the WWII net tender’s bow. Experimental at the time, it was a phenomenal success and was standard issue on later US Navy salvage ships.

(The modernized USS Cohoes (ANL-78) off Hawaii preparing to deploy to South Vietnam.)

The US Navy had two main tasks for USS Cohoes in Vietnam in 1968. The first was salvage work, specifically the sampans, junks, and small military watercraft sunk by the Viet Cong in South Vietnamese ports creating hazards to navigation. Some of this was recoverable gear, and during the ship’s first year in South Vietnam it was credited with salvaging $1 million worth of equipment.

(USS Cohoes (ANL-78) raising a sunken LCVP off the Vietnamese coast. These WWII landing craft were used as utility boats and river transports by the South Vietnamese navy.) (photo from All Hands, the US Navy magazine)

The second mission was upkeep of the POL Seaload System. The American military was consuming huge amounts of fuel, overwhelming the tanker piers in Saigon, Vung Tàu, Cam Ranh Bay, and Ða Nang. To alleviate this, underwater pipelines were laid allowing tankers to anchor offshore and pump directly to stations on land. These needed regular maintenance.

USS Cohoes operated in some very hazardous areas of I Corps, the northernmost military region of South Vietnam. One job, the raising of three sunken 100t barges, was near Cua Viêt only 6 miles from the DMZ. The ship was shot at from shore numerous times, including once by 122mm rockets. Beyond enemy action, it was also simply hazardous work lifting irregularly-shaped loads off the seafloor, or having divers do underwater welding in zero-visibility muddy waters.

USS Cohoes was awarded nine campaign medals and the Meritorious Unit Commendation. The ship was also decorated by the South Vietnamese government. The ship rotated back to the United States in 1971.

the Cohoes class abroad

Dominican Republic: In September 1976, three ships of this class were transferred to the Dominican Republic navy. During WWII, the D.R.’s navy had been disproportionately strong to the nation’s size and even into the Cold War era, was still a respectable force in the Caribbean. The ex-USS Eltah (AN-79) was renamed Cambiaso and remained in the WWII configuration.

The Dominicans did not intend to use the other two as netlayers, but rather patrol ships. The ex-USS Passaconaway (AN-86) was renamed Separación and the ex-USS Passiac (AN-87) was renamed Calderas. All net gear was removed, and the bow was rebuilt into a clipper-type bow. A second 3″ gun was mounted forward. Whatever existing radar was onboard was removed and replaced by a AN/SPS-64 modern search system, and modern marine-band radios installed.

(The rebuilt Separación on patrol in 1980.) (photo via Navypedia website)

These were useful and popular ships in the D.R. navy. Cambiaso decommissioned in 1997 and was used as a spare parts hulk for the two rebuilt ships. Calderas decommissioned in 2004 and Separación in 2006.

Haiti: The former USS Tonawanda (AN-89), which the US Navy retired in 1959, was leased to Haiti in 1960 as Jean-Jacques Dessalines for use as a buoy tender. The lease was 5 years and renewable under the Military Assistance Program (MAP).

(Jean-Jacques Dessalines in 1970.) (photo via navsource website)

The corrupt Haitian navy was one of the world’s worst and the ship accomplished little. It had already been refit with AN/SPS-5 radar in American service but was otherwise in WWII configuration. The lease was renewed several times until 1979 when it was sold outright for a nominal sum. The ship’s final fate is uncertain; one report said that it was scrapped in 1981.

Uruguay: USS Nahant (AN-83), the last net tender in the US Navy still doing net work, decommissioned in 1968 and was immediately transferred to Uruguay as ROU Huracan. It was a good deal for the Uruguayans as USS Nahant had received a refit while still in American service, with new radios and radar installed and the prototype of the scuba diver decompression chamber later fitted to USS Cohoes for Vietnam War use.  ROU Huracan was used as a search & rescue ship, a buoy tender, a scuba diver mothership, and a tugboat.

(ROU Huracan at sea.)

ROU Huracan was a successful addition to Uruguay’s small navy and served until January 1993. After that, the decommissioned warship was used as the meeting place for the Rio Uruguay Fishing Club. It was later sold to a civilian owner, and cut down and gutted into an immobile barge.

Venezuela: In 1962 – 1963, three were transferred to Venezuela: The ex-USS Marietta (AN-82) became ARV Puerto Santo, the ex-USS Tunxis (AN-90) became ARV Puerto Nutrias, and the ex-USS Waxsaw (AN-91) became ARV Puerto Miranda. All were transferred under renewable MAP leases, until being sold outright in 1977.

(ARV Puerto Santo in service. It was equipped with a AN/SPS-5 radar and enlarged superstructure. The WWII 3″ gun was retained.) (photo via navsource website)

Venezuela mostly used these ships for hydrography, research, and as buoy tenders. They were discarded in the late 1970s / early 1980s.

the passing of the net era

Thirteen days after the Nagasaki bombing, and with WWII not even formally over yet, the US Navy stated that it had a combined total of 7¼ miles worth of nets it wished to dispose of immediately with “….significantly more” coming after Japan’s formal surrender.

None of the three types had any possible civilian use. Furthermore the S and I types did not even have any scrap value.

Therefore the Surplus Property Board issued Special Order #18, authorizing the US Navy to abandon at sea or ashore unserviceable nets. Unused nets in storage were to be retained, and serviceable nets retrieved and cleaned. A large stockpile thus remained for post-WWII use.

There is no “one” reason why naval nets slowly died after WWII, but rather a combination of many small reasons.

Within the US Navy (and also other victorious navies) it wasn’t entirely crystal-clear in 1945 how effective anti-submarine and anti-torpedo nets had even been during the war. Certainly, when a base’s net defenses failed, that was readily apparent. For example in mid-1942 the Royal Navy established an elaborate net defense for Carlisle Bay on Barbados. None the less, U-514 breached it, sank one ship, and heavily damaged another.

During the 7 December 1941 attack on Pearl Harbor, five Japanese Type A midget submarines attempted to penetrate the partially-completed net array of the base. One tried to follow a ship through an open net gate and was sunk by USS Ward (DD-139) about an hour before the main air raid. Another made it through but was sunk by USS Monaghan (DD-354) in the channel. Two others never made it through. Wreckage of the fifth was found in 1992 with both torpedoes missing; it is believed that it made it all the way in, unsuccessfully fired at American warships, and later sank in West Loch.

Sometimes the results were open to conjecture. Sydney, Australia had an elaborate net array. On 30 May 1942, three Japanese midget submarines attempted to breach it and attack the target-rich environment. One became snarled in a net and sank, the second was detected while trying to breach the nets and sunk by depth charges, the third made it through and torpedoed HMAS Kuttabul before successfully making it back out (it was then presumably lost at sea). Whether Sydney’s nets “worked” is thus subjective.

Certainly nets did work sometimes. Germany and Finland cooperated to construct a huge, 19 NM-long continuous anti-submarine net in the Gulf Of Finland. Four Soviet Baltic Fleet subs were lost, either by being herded into adjacent minefields or by the net itself; and the net was never breached. The Soviets tried and failed to destroy it and only overcame it by relentlessly targeting net tenders and minelayers servicing it.

financial considerations

If there was one “main” factor, it was simply money.

Anti-submarine and anti-torpedo nets were not expensive on the lines of an Essex class aircraft carrier or a squadron of PBY Catalinas, but they were not cheap either. While it is challenging to calculate an overall expense, a good estimated WWII cost of the netting alone was $7.04 per linear foot ($69 in 2021 dollars). One must remember that just a single Type S panel was 300′ and just one net had multiple panels. Mile-long nets were common, and the San Francisco, CA net defenses used 7 linear miles during WWII. The spherical floats cost $451 ($4,428) and many were needed; a normal WWII government order was in 4,000-each production lots.

A related expense was tending laid nets. Nets needed regular maintenance in the water, resulting in at-sea days for net warfare ships. They were rated for waves 3′ to 5′; storms worse than that degraded or destroyed them.

(A Type T net destroyed by bad weather.)

Nets accumulated barnacles, algae, and general flotsam which had to be cleaned regularly, less it drag down the net.

(A net tender’s crew uses the fire hose to clean a Type T net.)

A cost difficult to quantify is passing down net skills after WWII. A recruit could reasonably trained on how to navigate with a sextant or clean a naval gun; all in a classroom setting. But net work was such a unique and odd thing, the only way to teach it was to actually do it repeatedly. As net tenders decommissioned and the number of net exercises declined, it became harder for chief petty officers to pass their net tending skills to young seamen.

Another intangible cost is the physical space nets took up in peacetime storage. Below is a small, temporary forward net depot during WWII.

The new technologies developed during WWII and then the 1950s required new workshops, training buildings, and warehouses ashore. At US navy bases, in lieu of tearing down WWII-era structures to make room, it was tempting to instead build atop dormant net weaving pads and often this was done.

(Ashore storage yard for the giant peg buoys used with the Type S nets.)

(Some WWII naval bases had a dedicated net ramp. As this art dwindled after WWII, these sometimes remained for years until the base’s budget allowed their demolition. By the 1970s, only “old salts” could remember seeing them in use.)

Finally there remained the problem of how to economically move nets in bulk. The four Indus class ships all survived WWII but were quickly decommissioned.

(The mothballed USS Indus (AKN-1) during the Cold War.)

Congress never funded their reactivation, and they sat unused until the 1960s and 1970s when they were finally scrapped.

new technologies

The Royal Navy invented a primitive indicator loop (IL) system in the waning months of WWI. In the 1920s and 1930s this was progressively developed, and further perfected by the British, the Australians, and the Americans during WWII.

An IL was simply a gigantic oval-shaped run of special cable laid on the seafloor. When a submarine passed over, its steel hull induced a small brief electrical current into the cable, monitored ashore. The above graph from an IL at Casco, AK during WWII shows the “dip” as a submarine passed over.  These were laid at important ports and bases. For example NYC had a half-dozen laid in a pattern as to be unavoidable and depending on an intruding sub’s course, it might possibly pass over multiple ILs allowing it to be tracked in speed and heading. ILs were more costly than a net on the front end, but once set on the seaboard were nearly indestructible and needed little upkeep.

During WWII the USA used the Mk18 offensive/defensive mine, with a 1,440 lbs warhead. Ideal for shallow water, these were magnetically fuzed, detonated by a vessel passing over. A defensive Mk18 field in a harbor could be marked by buoys to warn off friendly traffic and then just left alone; the Mk18 self-sterilized after 11½ months if not already swept.

Thousands were laid during WWII but many still remained in 1945. Unlike nets they could be stored in warehouses cheaply. Even after making the leftover WWII surplus available to NATO allies in 1949, there were still some in American storage into the Vietnam War era.

During WWII the US Navy began to consider a mine-based system like this not only as a complement to nets, but a replacement for them. The Mk51 defensive barrier mine system served with the postwar US Navy.

This hefty mine weighed 3 tons and had a 3,275 lbs warhead with magnetic fuze. Mk51s were laid in connected sets of thirteen spaced 150′ apart, and were controlled ashore by an operator equipped with binoculars and a radio. The operator could briefly turn the mines off to allow friendly ships to pass over. The Mk51 eliminated not only the need for a net gate, but also to even mark the barrier at all. Unlike net buoys which could be spotted from the air or through a periscope, there would be no way for an enemy to know where the barrier was or even if there was one. The cheap Mk51s could sit unattended on the seafloor for over a year.

Four months after WWII ended, the US Coast Guard tested the XCF dunking sonar aboard a HOS-1 Hoverfly II. During WWII the USCG had already made enthusiastic use of early helicopters, and now this opened up an entirely new field of anti-submarine detection.

(XCF dunking sonar on a US Coast Guard Hoverfly II.)

During the early 1950s, the US Navy integrated the AN/AQS-1 dunking sonar onto the HUP-2S Retriever. Obviously the flight-hour costs of a helicopter are high, proportionally higher than even a net array, but the difference being that the helicopter was mobile and could perform any number of other tasks.

No one of these things “replaced” anti-submarine nets per se, but together and in combination with the other factors, they sort of did just that.

a changed threat

When WWII began in 1939 submarines were not particularly high-tech, and were basically small surface warships which submerged for short durations. By the end of WWII in 1945, new submarines had snorkels, radar, sonar, and were a much more expensive proposition. It was considered less likely that a navy would put a modern large submarine tailored for open-ocean warfare, into a high-risk harbor intrusion mission.

(U-47 in 1939. It was a Type VIIB displacing 857t with a submerged speed of 7½ kts. It sank HMS Royal Oak after penetrating Scapa Flow in WWII’s second month, before the Royal Navy had time to complete the net array there. Neither U-47 nor Scharnhorst in the background survived WWII.)

(U-3008 three years after WWII, during its evaluation by the US Navy. A Type XXI, it displaced 1,819t and could make 17 kts submerged. It was scrapped in 1956.)

Some of the biggest failures of nets during WWII were caused by midget submarines and underwater chariots. When they succeeded these missions were spectacular, but they masked the high cost in money and the appalling loss rate, both in action and in training. After WWII, things like this certainly retained a home in the SpecWar communities both east and west, but weren’t really an emerging threat any longer.

As far as anti-torpedo nets, the era of torpedo aircraft surprising an anchored fleet like at Taranto or Pearl Harbor had totally faded away. Air defense radars were now common, surface-to-air missiles were being developed, and facilities were on constant alert during the Cold War.

(The SCR-582 was an early harbor defense radar used during WWII. It could detect ships or low-altitude planes, or with the antenna canted up, high-altitude planes. It could also detect a surfaced submarine at 17 NM at night or in bad weather meaning that for a harbor incursion mission, the attacking sub would not only have to be submerged while evading nets, but also approaching and departing the coast, further depleting its battery.)

the final end

The closure of the Tiburon facility in 1958 was the swan song of US Navy nets. Although they remained in use, nets and net tenders were now spread sporadically around the fleet and not really a core discipline any longer.

(Naval reservists drill with a WWII Type T net at Indian Island, WA after the Korean War.) (photo via The Leader newspaper)

By the mid-1960s, all but USS Butternut of the Aloe class were in mothballs or transferred abroad. Of the Cohoes class, only USS Nahant, USS Cohoes, and the modified cable hull were still in active US Navy use, while the whole Ailanthus class was already long gone. By then only USS Nahant (AN-83) was still regularly handling nets. It was doing other tasks (towing, buoy tending, scuba support) as much if not more than net exercises by then. USS Nahant decommissioned in 1968.

(USS Nahant (AN-83) conducting a net drill off the east coast in 1961. President Kennedy personally observed this particular drill.) (photo via navsource website)

As the 1970s dawned there were still WWII netlayers in mothballs. With little hope of further use, these began to head to the shipbreakers. This really picked up when President Ford took office in August 1974. A WWII veteran himself, Ford sought to root out waste at the Pentagon and one thing that irked him was the upkeep costs on the US Navy’s mothballed ships. In particular, there seemed little sense in keeping netlayers and they dwindled rapidly.

(photo via navsource website)

Above is the Aloe class ex-USS Palm (AN-28) at Hatch & Kirk’s pier in Washington state during 1971. USS Palm served in both the Atlantic and Pacific during WWII. Decommissioned in 1946, USS Palm was never reactivated and was finally disposed of in June 1971. Hatch & Kirk was (and is today) a unique and well-run company. Founded in 1945, its original niche was buying disposed WWII US Navy warships and extracting engine parts from the plethora of manufacturers the USA used during WWII. Parts for many of these 1930s and 1940s engines, including USS Palm‘s Enterprise DSG-6, went out of production after WWII ended and as years passed, entire companies vanished.

Hatch & Kirk was an invaluable in keeping WWII-generation warships going decades after WWII ended and the original manufacturer had ceased parts support or gone bankrupt.

(The ex-USS Buckeye during the early 1980s.) (photo by Chris Howell)

USS Buckeye (AN-13) was another Aloe class never reactivated after decommissioning in 1947. During the Ford administration, it was shed from the Suisun Bay, CA mothball fleet and towed to Hawaii. There it was used as a salvor’s exercise hulk, being repeatedly sunk and raised until it was worn out.

The last netlayer in the US Navy, USS Cohoes (ANL-78), was not desired for continued use after returning home from Vietnam and never handled nets during or after that deployment. USS Cohoes decommissioned in 1972 and was scrapped in 1973. For the US Navy the era of net tenders was over.

postscript

Abroad, WWII nets remained in diminishing use longer. The Royal Navy generally followed the same timetable in phasing out WWII nets as the US Navy, but some remained in storage as late as the 1970s. The Egyptian navy had some in use during the Six-Day War.

(The Bar class were the main Royal Navy net tenders, which were called boom defense vessels in the commonwealth. HMS Barcross transferred to South Africa after WWII and as SAS Somerset, served until 1986. Now a museum ship, as of 2021 this is the last WWII net warfare ship in the world.)

Argentina and Chile almost went to war in December 1978. To help protect their aircraft carrier ARA Veinticinco De Mayo (the HMS Venerable of WWII) from Chilean missiles, the Argentines planned to adapt Type T netting to be hung like curtains around the carrier’s hull above the waterline. The netting had been imported decades earlier to protect Argentina’s two American-built battleships, long since scrapped. Diplomacy prevented the war. It’s doubtful the idea would have worked.

During the 1980s, Sweden still made use of anti-submarine nets. Cut and tampered nets were presented as evidence that foreign submarines were operating in Swedish waters. In 1981 the Soviet submarine S-363 ran aground near Karlskrona naval base, and there was no longer any need to convince skeptics with cut nets.

France had a stockpile of WWII netting at Toulon into the 1990s. The Greek navy still had some leftover WWII nets into the 2000s on the island of Crete. In the 2020s, the South Korean navy still makes use of barriers of this type, although it’s unlikely they date to WWII anymore.

(After the Japanese attack, the US Navy built a net depot right at the mouth of the channel into Pearl Harbor, in addition to the one actually on the base. Known as Bishop Point, this early 2000s photo shows it now in use by MDSU-1, a salvage scuba unit at Joint Base Hickam, HI.) (Library of Congress photo)

The WWII US Navy’s forgotten “final piece of the puzzle”, the gate vessels, actually outlived both the seagoing net tenders and nets themselves.

(YNg-27 blown aground by a storm in 1956. By then the WWII armament had been removed, however the AN/QBE-1 sonar added during WWII was still aboard. This tough service craft shrugged off the grounding and continued in service until 1974.) (photo via navsource website)

The YNg craft were strongly constructed and made ideal conversions to other barge types as the net warfare era ended during the 1960s.

(YNFX-15, shown here in 2014, was formerly YNg-22 during WWII. It was rebuilt with a new superstructure in 1965 as a “special-purpose non-propelled lighter” for scuba divers. As of June 2021 it is still in US Navy service, now 80 years.) (photo via shipspotting website)

Certain relics of the US Navy’s WWII net program still survive. Building 77 at Naval Magazine Indian Island, WA is now used for other purposes. During WWII it was one of the original assembly points for Type T nets.

None of the American WWII netlayers were preserved.

(US Navy net warfare motif during WWII.)

 

Advertisement