Atlantic Convoy Escort

I vacation in Virginia Beach. There used to be a plaque on the boardwalk honoring HMT Kingston Ceylonite which was lost to a mine offshore. The plaque was at 24th Street in front of the Coast Guard Museum in the former life saving station. When the boardwalk was reconstructed several years ago the plaque disappeared. I asked the museum staff about it and also wrote to the city and the local newspaper, but no one seems to know what happened to it. Sad to lose a bit of history.

 

Thanks for scrounging this up! One point that doesn't seem to have been addressed - frigates, destroyer escorts, etc. are usually presented as smaller, cheaper alternatives to destroyers, which they were, but more importantly, they were specialized anti-submarine ships, and in that mission area the best of their era. Most notably they carried forward-firing weapons like Hedgehog which were almost never found on fleet destroyers during WWII. Escorts also carried up to eight depth charge throwers and 200 depth charges, far more than any DD. Indeed depth charges were often one of the items reduced in order to mount additional antiaircraft weapons and other destroyer priorities.

The difference is probably best illustrated by those destroyers which were modified for escort duties. This involved reduction of main armament and torpedos in favor of additional DCs and sometimes Hedgehog. Often speed, i.e. a boiler, was sacrified in favor of more fuel/range. The result was a fine antisubmarine ship; almost every distinct capability of a destroyer was in excess of what was required for the escort role.

Probably the best antisubmarine ship of the war was the Loch class frigate, due to the Squid, the most advanced AS weapon of the war, and the Type 147 sonar, the first which could directly measure target depth. Otherwise the DE would be #1.

<Squid was so effective that the Loch and Castle classes dispensed almost entirely with conventional depth charges, carrying only 15 with two throwers, three 5-charge patterns>

The question was posed If sloops, corvettes, frigates, and so forth are better ASW escorts, why were they never assigned to fleets and task forces? For a start, it would hardly be possible for 20-knot ships to escort carriers, cruisers, or even modern battleships. More to the point, the 'escorts' were intended to participate in surface or air actions; there was no role for a pure antisubmarine ship in a carrier task force or surface action group. There really were two distinct types of combat. Against merchant shipping, submarines practiced something akin to guerilla warfare. They could strike anywhere, so convoys needed to be escorted even though most of them never even came under attack, even at the height of the U-boat campaign. There were vastly more merchant ships than there could ever be escorts, and the half-dozen or so escorts of any given convoy had to be capable of fighting a prolonged battle if their convoy was the one to come under attack. This called for large numbers of escort ships with maximum antisubmarine capacity. On the other hand a fast-moving, heavily armed task force was unlikely to come under sustained submarine attack. Destroyers outnumbered both their own heavy ships and any potential attacking submarines; they could provide a reasonable level of antisubmarine defense even if they were not individually the most capable AS ships.

The British evolved an interesting mix of escort ships. They had the corvettes to provide the simple numbers needed. Frigates and destroyers, especially those converted to escort configurations, were the 'capital ships' of ASW. Sloops were also top of the line AS ships, but the modern ones like the Black Swan class added AA capability for situations in which both air and submarine attack were possible.

The terms sloop, corvette, and frigate date from the days of sail, denoting similar type ships, progressively larger and more powerful. Corvettes and frigates were replaced by what came to be called cruisers, but a few sloops hung on, mainly for their utility in patrolling distant reaches of empire. The RN built its last sailing sloops (also with steam engines) in the 1890s, and a dozen or so will still active in WWI although their sailing rig had been removed. The war brought a need for small, simple ships of similar size and capabilities, and the name 'sloop' was retained although the new ships had never had sails. Incidentally the WWI sloops were known as the Flower class. They proved useful as escorts and minesweepers and continued to be constructed in small numbers between the wars; they became progressively more sophisticated with warship features like steam turbine engines and heavier armament. Ironically by 1939 there was a need for something smaller and cheaper than a sloop, so the term 'corvette' was resurrected, as were the Flower names. An improved follow-on, originally termed a "Twin Screw Corvette" became the frigate.

 

Carronade: By the late war I will grant that dedicated ASW escorts have significant advantages. I was discussing the early war period of 1939-1942 before forward throwing contact projectors like Hedgehog were widely available. I think all of us can agree that the Royal Navy practiced superior ASW during the early war period. Freebird had made the contention that the USN's ASW capability deficit in late 1941 was at least partially material, since he claimed USN escorts were primarily restricted to fleet destroyers, which he called less capable. I argued that the USN's lack was far more doctrinal. In so doing I made several points; listing numerous escorts beyond fleet destroyers, enumerating the more limited US ASW needs, and arguing that fleet destroyers were, at that time, of roughly equal ASW capability. You seem to take issue with this last.

In 1941 a typical ASW escort, like an early Flower class corvette generally had two depth charge rails and perhaps as many as four projectors. Hedgehog only became available in late 1942 and Squid in 1943. Neither was fitted to any escort, dedicated ASW or otherwise, until well after the time I am considering, and thus they are irrelevant to the specific question. Increased depth charge stowage is also a rather later war factor. The first run Flowers carried perhaps 100 depth charges

You cite longer range as one advantage of dedicated ASW escorts and discuss removing boilers, sacrificing speed for bunkerage. While this was done, you can hardly call the ships thus converted typical fleet destroyers. They were primarily surplus V and W class destroyers left over from the First World War. These were rather short legged, say 3500 nmi or so at 15 knots, and particularly so at high speed. Interwar fleet destroyers had longer ranges, particularly those designed for the Pacific. Strangely, early purpose built ASW escorts were often nearly as short ranged. 5000 nmi was a much more typical range for a late interwar fleet destroyer and 3500 was more than adequate for Atlantic convoy duty. I believe the removal of the boilers had as much to do with improving living conditions as it did with increasing range.

War built destroyers generally had six K-guns, two depth charge rails, and increased depth charge capacity. As the war progressed, the ASW capabilities of fleet destroyers increased in parallel to that of dedicated ASW escorts. It's a little disingenuous to compare late war frigates with early war destroyers. And while it's true that fleet escorts sacrificed something in the way of depth charge stowage for anti aircraft, it's equally true that fleets in the Pacific faced a much greater air threat than convoys in the Atlantic and rather less of a submarine threat.

The argument that a 20 knot escort can't keep up with a 30 knot fleet loses something when you consider that most fleets cruised at around 20 knots and when attacked by submarines it was quite typical for the main combatants to dash ahead leaving one or two destroyers to face the threat and catch up later. Further, the US in particular had fleets that operated at lower speeds. Rather than dedicated ASW platforms, they were escorted by a mix of fleet destroyers and DEs, which retained the AA and much of the surface armament of a full fleet destroyer but sacrificed speed for economy.

I took Freebird's statement about capability to have something to do with more than just capacity, to suggest that somehow he believed that sloops and corvettes were better ASW platforms by their very nature than fleet destroyers; better able to sink a given submarine. I don't see that. I can easily see why fleet destroyers have lots of capabilities you don't need to escort a convoy. Makes sense. They're combatants in their own right. But if you could have a fleet destroyer for the same price, which one would you buy?

. . .

Ergo the big advantage of the Sloop/Frigate/Corvette/Fishing trawler with a depth charge rack is economic.

You get similar ASW capabilities on a much cheaper hull. The greater capacity is, I think, more a reflection of the threat environment than anything else. The air threat was quite limited and the surface threat was virtually nonexistent, so the need for such weapons systems was minimal and the tonnage they would have required was better used for more depth charges. Of course, such a ship would be of very limited utility in any other threat environment, since it would be so very very vulnerable to anything else. (The obvious downside to specialized weapons systems: they're great at what they do, but usually nothing else.)

In any event, I don't think we substantially disagree about anything, we're just talking past each other.

 

You cite longer range as one advantage of dedicated ASW escorts and discuss removing boilers, sacrificing speed for bunkerage. While this was done, you can hardly call the ships thus converted typical fleet destroyers.

Indeed not. My point was that they ceased to be "typical fleet destroyers" when modified for ASW. I agree there was not as much difference between destroyers and escorts early in the war as there would be later, but even then it was recognized that the fleet destroyer was not the best ASW platform - otherwise why did the RN take half the guns and torpedos off the surviving A-I types as soon as they could be spared from duty with the fleet?

Starting in 1941, another common modification was replacing the director control tower with the Type 271 radar 'lantern'. This left the remaining 4.7s with local control only, but that was considered sufficient for engaging surfaced U-boats. Needless to say no fleet destroyer had her gunnery control crippled in this manner.

If we agree that there was little difference early in the war, we cannot also say that the ASW capabilities of fleet destroyers increased in parallel to that of dedicated ASW escorts. The difference became more profound as the war went on, most notably the Hedgehog and Squid discussed earlier. With a few exceptions like the mounting of Mousetrap in twelve Benson class DDs, the only ASW improvement to destroyers was more depth charges. Conversely the DC supply was often reduced in favor of AA weapons, radar, and other wartime necessities - although the number of K guns might stay the same, resulting in a decrease in number of patterns that could be dropped.

The argument that a 20 knot escort can't keep up with a 30 knot fleet loses something when you consider that most fleets cruised at around 20 knots....

You're not serious?? Of course fleets cruised at economical speed when they didn't need to go faster, but screening ships always had at least few knots speed advantage over the heavy units. You're not actually suggesting that the reason for having destroyers with the battle fleet rather than sloops was their ASW capability?

Slower forces like CVE groups or amphibs were escorted by a mix of DDs and DEs when the surface and AA capabilities of DDs were needed. Although we've jumped around a bit, I thought we were in agreement that the DE was a superior ASW ship, even to late war DDs? However, the difference in gunnery was greater than the numbers (two 5" vs. 4-6) would suggest since the DE lacked the dual-purpose gunfire control system of the DD.

In the prewar years, there was an expectation that the fleet destroyer would be the primary ASW platform; even the RN built only small numbers of sloops. The development of sonar allowed navies to think they had the submarine problem licked; there was a belief that a couple of ASDIC-equipped escorts would suffice to protect a convoy or capital ship (this was also reflected in the cautious tactics of prewar and early war submarine doctrine). Mainly by default, most of the submarine fighting and killing early on fell to destroyers.

 

You can make a fleet destroyer to perform decent ASW, but you are correct, the corvettes were cheaper and could be built by mercantile yards.
The problem with the US DD's was that there were a limited number of modern ones (100 or so IIRC), and the rest were the old "flush deckers" which were wet, had a larger turning radius and most weren't ASW modified.

They did modify about a dozen or so of the WWI DD's, but there were 70 or 80 left (after giving the 50 oldest to the UK) which hadn't been upgraded.
Now, had they been modified by Dec 1941, it would have been much better, but as it was they were almost useless.
(Presumaby that's why they were often left in port during the spring/summer of '42, as the USN didn't have any confidence is there ASW ability)

 

Here's something I posted a while back about the WWI-era DDs:

The original armament of the flush-deck/four-piper destroyers was four 4"/50 cal guns, one 3"/23 AA, and four triple 21" torpedo tube mounts. By WWII they also carried depth-charge racks and several water-cooled .50-caliber machine guns. They had four boilers in two boiler rooms.

In 1941, 48 were in service in other roles:
18 DMS minesweepers
8 DM minelayers
14 AVD seaplane tenders
6 APD fast transports
2 training/experimental: Semmes attached to Submarine School, Dahlgren to Key West Sound (sonar) School

Many had already been scrapped including the first generation of DMs.

DMs, DMSs, and the later antisubmarine conversions had #4 boiler replaced by fuel tanks; being close to amidships, this was the best location for a variable weight not originally provided for. AVDs and APDs had the forward boiler room converted to accommodations, storage, and gas tanks in the AVDs. This was more convenient since it was adjacent to existing living and working spaces; the deck immediately above, between the bridge and the midships deckhouse, was also filled in to provide additional space.

The destroyers-for-bases deal left 71 flush-deck DDs, 37 in the Atlantic (reduced to 36 by the loss of Reuben James in October 1941), 21 Pacific, 13 Far East. Most of the Atlantic and Pacific ships were assigned by division or squadron to naval districts, as was the one remaining older destroyer, the "thousand-tonner" Allen (DD-66) at Pearl Harbor. Prior to hostilities, 27 of the Atlantic units were modified for escort duties, with six 3"/50 DP guns replacing the four 4" and the aft pair of torpedo tubes. The 3"/23 was also dispensed with and six depth charge throwers added.

Wartime modifications were less extensive, although the replacement of #4 boiler by fuel tankage was common. Some ships including the eight survivors of the Asiatic Fleet had the aft torpedo tubes replaced by DC throwers but retained 4" armament. Up to six 20mm guns were added, replacing .50s. Many of the converted types like DMSs and APDs received 3"/50s in place of 4"; this was particularly important in the Pacific where they faced air attack. Some also received 40mms, either one twin power-operated mount or two manually operated singles.

The only major wartime conversions were additional APDs which proved very useful. Approximately 20 DDs and several AVDs were converted.

Blair's Hitler's U-Boat War lists 92 destroyers in the Atlantic Fleet on 12/7/41: 55 modern types including all 28 of the new Bensons then in commission and 37 flush-deckers including Dahlgren. The number remained relatively consistent over the next few months although individual ships transferred to the Pacific and new ones were commissioned in East Coast yards. The Pacific (including Asiatic) had 46 modern and 35 older DDs, total 81.

All but ten of the LantFlt flush-deckers had been modified for ASW and were active in that role; in fact one of them, Roper, scored our first U-boat kill, U-85 on April 13-14, 1942. While double-checking this I ran across an instance of her escorting a convoy to Londonderry. Blair also lists the escorts of troop convoys, which included both modern DDs and flush-deckers; the priority given to troop convoys was one reason for the dearth of escorts for other shipping.