Rn vs IJN

[EwenS]

Its also worth remembering that their tends to be a lot of emphasis on the destroyer, when the key anti submarine vessel is the Frigate/Corvette/Sloop. Of these, the RN alone had hundreds of ships (excluding A/S Trawlers) supported by escort carriers and a significant Coastal Command. Compared to this, the IJN had next to nothing.

While the Japanese started late in the escort they built rather more than is sometimes appreciated and were still completing them as late as July 1945. For example

Japanese Escorts

Japanese Subchasers

And those are only the purpose built ships. They also took over large numbers of captured and salvaged vessels. Again by way of example

Japanese Patrol Boats

By the way I'm not arguing that they were as numerous nor anywhere near as effective as Allied AS craft, just that they were more numerous than is sometimes appreciated.

 

[Alan Stevens]

The record of Japanese destroyers in the ASW role was pathetic. Being a USN submarine was a dangerous job but it was safer than being in any other navy thanks to Japanese incompetence, The USN only lost 52 submarines in the entire war including accidents and friendly fire.. This is the lowest loss of all the major navies. THe USN did an accounting after the war and found that only 41 could be attributed to the Japanese (including mines). The destroyers where given credit for 4 of these kills with 1 shared with aircraft and 4 possibles. Giving the destroyers the benefit of the doubt gives only 9 in total. To give that low number some perspective Royal Navy's submarines sunk 38 enemy subs. RN destroyers sunk 90 submarines in the North Atlantic alone.
The Japanese destroyers also has a losing recorded against USN subs. USN subs are given sole credit for 23 destroyers. You were safer in a US sub than in a Japanese detroyer.

There was nothing safe about being on a Japanese destroyer!

 

[WARSPITER]

From reports of actions I have read the Japanese tactic was to charge an enemy sub when detected with as many vessels
as they could. This ruined any sounding capability and allowed the sub to move out of harms way.

Depth charges would be sent down all over the place with the sub being counted as neutralised if it didn't poke it's head up.

Purpose built escorts carried far more depth charges than destroyers (typically 120 as opposed to 30) but that didn't
seem to help as the tactical use was not good and was not updated, unlike the allied ASW which evolved all the way through the war.

 

[Geoffrey Sinclair]

IJN. Ignoring the 250 or so wartime CHA types, at around 130 tons each.

CH type Submarine Chasers, normally around 300 to 450 tons displacement, all up 64 built, starting in 1933. As of end November 1941, nominal strength 26, with 3 more added in December, in 1942 it was 12 added and 2 lost, in 1943 it was 14 added and 2 lost, in 1944 it was 9 added and 19 lost, in 1945 19 lost, August 1945 strength 22. Peak strength 53 in January 1944, first 2 losses in July 1942, last one built in October 1944.

Escorts, the C and D class, 800 to 900 tons, plus captured ships, there were 4 built in 1940/41, HMS Thracian was added in 1942, in 1943 17 added and 2 lost, in 1944 91 added and 21 lost, in 1945 66 added and 58 lost. End 1943 strength 20, end 1944 strength 93, peak strength of 109 in June/July 1945, down to 98 end August. First loss in September 1943.

Salvaged allied ships included above, P101 (HMS Thracian), P102 (USS Stewart), P103 (USS Finch), P104 (Dutch Valk), P105 (US Philippines Arayat), P107 (USS Genessee), P108 (Dutch Arend), P109 (Dutch Fazant)

IJN "DE" first arrival April 1944, first loss August 1944, 17 built in 1944, 15 in 1945, 13 lost, peak strength 24 in May/June 1945.

Older IJN destroyers, 55 in November 1941, down to 9 in August 1945.

Fubuki and other larger destroyers, 68 end November 1941, 9 in August 1945, peak wartime strength 69 in June and August 1942. One destroyer added and 2 lost in December 1941, in 1942 10 added and 15 lost, in 1943 12 added and 26 lost, in 1944 7 added and 41 lost, in 1945 2 added and 7 lost. End 1942 strength 62, End 1943 strength 48, End 1944 strength 14.

 

[Thumpalumpacus]

All Japanese depth charges had dimensions of 30.5" by 17.7" (77.5cm by 45cm). The Type 95 was standard at the time war broke out, with a 220 lb (100 kg) charge of Type 88 explosive (ammonium perchlorate and ferrosilicate). Its fuse had a water inlet that detonated the charge when a certain amount of water had entered. There were just two depth settings, 100 feet (30m) and 200 feet (60m), the latter well above the dive depth of American subs. Later the charge was increased to 324 lb (147kg) of Type 97 explosive (70% TNA/30% HNDA) and a 300 foot (90m) setting was introduced. Slow ships could drop the charge with a parachute to retard its sinking until the ship was clear, but this reduced the depth setting to a maximum of 100 feet (30m).

The Pacific War Online Encyclopedia: Depth Charges

 

[Wild_Bill_Kelso]

x

 

[Glider]

While the Japanese started late in the escort they built rather more than is sometimes appreciated and were still completing them as late as July 1945. For example

Japanese Escorts

Japanese Subchasers

And those are only the purpose built ships. They also took over large numbers of captured and salvaged vessels. Again by way of example

Japanese Patrol Boats

By the way I'm not arguing that they were as numerous nor anywhere near as effective as Allied AS craft, just that they were more numerous than is sometimes appreciated.

Many thanks for the link, much appreciated.

 

[Shortround6]

I would note that the British pretty much started the war with one or two rails plus a pair of depth charge launchers which allowed for a 4 charge diamond shaped pattern and they often used two different depth settings in the same pattern. This was superseded by 7 charge pattern ( four side launchers) and then a 10 charge pattern (late war?) with 6 side launchers and they ended the war with a 14 charge pattern that required 8 side launchers. A lot of American DEs got 8 K guns (side launchers) but I don't know if they used all 8 at once or split them into two salvos.
At any rate this rather shows the even 30-32 depth charges per ship was a rather scanty allotment. Keeping a sub down is a lot different than killing it.

The crappy US torpedoes may have helped cover up the poor Japanese Anti sub capability.
The US subs in 1942 weren't actually sinking that much (Japanese shipping). If the US subs had actually been sinking more ships perhaps the Japanese would have put more effort into better weapons/techniques earlier?
Nobody likes loosing ships but if the losses are acceptable/sustainable then there isn't as much R&D or even panic fitting of weapons to stop high losses.

 

[EwenS]

The RN 10 charge pattern became standard fairly early on in WW2, where topweight and other considerations allowed. For example the Flower class started with 2 rails and 2 throwers, but when from late 1940 the modifications to fit them as ocean escorts (e.g. lengthened forecastles etc) also saw an extra 2 throwers being added.

The 14 charge pattern (2 rails & 8 throwers) was not very common and was quickly phased out. The River class frigates designed from late 1940 were designed for it, with the first completing from spring 1942. But this from "River Class Frigates and the Battle of the Atlantic".

" It was not long before the fourteen-charge pattern came under some criticism. In November 1942, trials were carried out with the destroyer HMS Skate, and these showed that the charges interfered with one another, and some failed to explode because of this. Furthermore, the effect of the four extra charges did not justify the weight of the throwers and their equipment on the decks of a ship. The fourteen charge pattern was abandoned before the majority of the River-class had come into service, and the ten-charge pattern became standard."

That standard armament can be seen on sloops, corvette, frigates and wartime built destroyers to the end of the war. It was adopted for the wartime built destroyers from mid-1942 as an amendment to the original design. The 4 L class destroyers given 4" guns completed Dec 1940-Jul 1941 received 8 throwers and 3 rails.

As the Battle of the Atlantic wore on, and such was DC expenditure, that extra storage racks began to be fitted to AS ships where possible to store additional depth charges. These can often be seen along the sides of the quarterdecks of Rivers and Captains. Another practice saw stern rails being lengthened. So for example a River class saw its DC load increased from 100 to 200 as the war progressed.

The introduction of the Squid AS mortar from late 1943 firstly on the Castle class corvette (single Squid) and then the Loch class frigates (double Squid) saw the DC equipment on these ships drastically reduced to 2 throwers, 1 rail & only 15 depth charges. Squid coupled to the new ASDIC sets then appearing proved to be the best AS weapon of the war.

Topweight problems began to hit the standard RN intermediate destroyer design by mid-1944. So the 1942 C class of the Ch, Co & Cr flotillas had to sacrifice some DC armament, amongst other things, to gain the new Mk.VI director. They only had 2 rails, 2 throwers and 35 DC. They began to enter service from mid-1945.

 

[Shortround6]

Thank you.

There were a number of things going on in the Atlantic and with Destroyers and smaller they can never get what they want into the small hulls.
The Corvette started as the Whale Hunter, an improved (faster) Trawler.
Early drawings show the 4in and single 2pdr for guns and two 12 charge DC racks on the stern and two throwers with 16 DC stowed on the decks. However none (?) were completed to this standard. Earlier drawings/plans show different armament and different crews and range. By April 1941 the RN was calling for four throwers and a total of 60 DC. MGs were added, swapped, moved, replaced by 20mm guns and so on.
The 20kt Frigates had a design/development phase during which things were shift around. In Dec 1940 they were calling for eight throwers with 32 charges, 30 charges on the rails and at least 38 charges in the magazine.

At this time the RN was fooling around with several ahead throwing weapons. But there is a difference between development and service. It does show that the RN was not even happy with the 14 charge pattern however.
They also were not happy with Flower class corvette. Aside from the lack of speed (and 15kts was a whole lot better than 11-12kt trawlers) they rolled too much which affected their ability to use sonar. Of course early Sonars could not be used at much over 15kts so the extra speed of Destroyers only came into play in very limited circumstances.

Destroyers, if they are to retain their other capabilities, actually make pretty poor ASW ships. This is at a given point in time like WW II when the Destroyers were optimized against surface ships using torpedoes. This was further complicated in WW II by the need to increase AA armament, many times substantially. This limited the amount of DCs and throwers that could be mounted without sacrificing either torpedo tubes or main surface guns.

The RN had crap load of old destroyers that they could pull at least one set of tubes off, and 1-2 4in-4.7 guns and mount more DC on (and swap in a few AA guns) without sacrificing battle fleet needs. This helped fix the image of the Destroyer as an AS ship. Some of the Old Destroyers even had a boiler taken out (sacrificing speed) for range.

The Japanese did not have enough destroyers to do that with. Or at least not many/enough. And they were nowhere near as good as purpose built ships. Japanese also used the pull a boiler trick at times.

 

[Reluctant Poster]

Thank you.

There were a number of things going on in the Atlantic and with Destroyers and smaller they can never get what they want into the small hulls.
The Corvette started as the Whale Hunter, an improved (faster) Trawler.
Early drawings show the 4in and single 2pdr for guns and two 12 charge DC racks on the stern and two throwers with 16 DC stowed on the decks. However none (?) were completed to this standard. Earlier drawings/plans show different armament and different crews and range. By April 1941 the RN was calling for four throwers and a total of 60 DC. MGs were added, swapped, moved, replaced by 20mm guns and so on.
The 20kt Frigates had a design/development phase during which things were shift around. In Dec 1940 they were calling for eight throwers with 32 charges, 30 charges on the rails and at least 38 charges in the magazine.

At this time the RN was fooling around with several ahead throwing weapons. But there is a difference between development and service. It does show that the RN was not even happy with the 14 charge pattern however.
They also were not happy with Flower class corvette. Aside from the lack of speed (and 15kts was a whole lot better than 11-12kt trawlers) they rolled too much which affected their ability to use sonar. Of course early Sonars could not be used at much over 15kts so the extra speed of Destroyers only came into play in very limited circumstances.

Destroyers, if they are to retain their other capabilities, actually make pretty poor ASW ships. This is at a given point in time like WW II when the Destroyers were optimized against surface ships using torpedoes. This was further complicated in WW II by the need to increase AA armament, many times substantially. This limited the amount of DCs and throwers that could be mounted without sacrificing either torpedo tubes or main surface guns.

The RN had crap load of old destroyers that they could pull at least one set of tubes off, and 1-2 4in-4.7 guns and mount more DC on (and swap in a few AA guns) without sacrificing battle fleet needs. This helped fix the image of the Destroyer as an AS ship. Some of the Old Destroyers even had a boiler taken out (sacrificing speed) for range.

The Japanese did not have enough destroyers to do that with. Or at least not many/enough. And they were nowhere near as good as purpose built ships. Japanese also used the pull a boiler trick at times.

In his book "Atlantic Escorts" D K Brown lists the following sinkings of U-boats by class

Destroyers
Modern 9
Inter-war A-I 39
Older (WWI) 26
Towns (Ex USN) 8
Hunt 8

Sloops
Black Swan 28
Older Sloops 12

Frigates
River 22
Loch 12
Captain (US DE) 28
Colony
(US built River) 5

Corvettes
Flower 38
Castle 5

The destroyers as a group were very successful accounting for over 1/3 of the total. The inter-war classes (up to the Tribals and Js) had the highest number of kills. When considering that the majority of them were engaged in other duties this really stands out.

The "crap load" of destroyers that were heavy modified were the WWI vintage V and W classes.

 

[EwenS]

In his book "Atlantic Escorts" D K Brown lists the following sinkings of U-boats by class

Destroyers
Modern 9
Inter-war A-I 39
Older (WWI) 26
Towns (Ex USN) 8
Hunt 8

Sloops
Black Swan 28
Older Sloops 12

Frigates
River 22
Loch 12
Captain (US DE) 28
Colony
(US built River) 5

Corvettes
Flower 38
Castle 5

The destroyers as a group were very successful accounting for over 1/3 of the total. The inter-war classes (up to the Tribals and Js) had the highest number of kills. When considering that the majority of them were engaged in other duties this really stands out.

The "crap load" of destroyers that were heavy modified were the WWI vintage V and W classes.

Re the Black Swans - 16 U-boats were sunk by Captain F Walker's 2nd Support Group between May 1943 and his death on 2 July 1944. All these kills were by Black Swan class vessels in the Group. The Group subsequently achieved 6 other kills but from June 1944 included ships of other classes.

It also needs to be remembered what periods of time these classes operated over. For example the first Loch class frigate only completed in April 1944 with only 21 ships completed by the end of the European war. Yet they achieved 12 kills. The 21 Colony class frigates were delivered Oct 1943 -Jun 1944.

And also the areas that they operated in. The inter-war sloops spent much of their wartime careers on the routes to/from Sierra Leone where there was less U-boat activity so less opportunity for U-boat kills. Most of the Towns found themselves relegated to the east coast convoy routes from mid-war where there was little U-boat activity until late in the war.

 

[Reluctant Poster]

Re the Black Swans - 16 U-boats were sunk by Captain F Walker's 2nd Support Group between May 1943 and his death on 2 July 1944. All these kills were by Black Swan class vessels in the Group. The Group subsequently achieved 6 other kills but from June 1944 included ships of other classes.

It also needs to be remembered what periods of time these classes operated over. For example the first Loch class frigate only completed in April 1944 with only 21 ships completed by the end of the European war. Yet they achieved 12 kills. The 21 Colony class frigates were delivered Oct 1943 -Jun 1944.

And also the areas that they operated in. The inter-war sloops spent much of their wartime careers on the routes to/from Sierra Leone where there was less U-boat activity so less opportunity for U-boat kills. Most of the Towns found themselves relegated to the east coast convoy routes from mid-war where there was little U-boat activity until late in the war.

The Lochs had a huge advantage when they arrived on the scene. Much better radar, much better asdic, a far superior ASW weapon in the Squid, much better air support and last but not least years of experience to draw on. The tough sledding was done by destroyers and corvettes.
May 1943 was the turning point in the Battle of the Atlantic when Doenitz was forced to call off the wolfpacks, after that it was basically clean up. Looking at the Uboat looses in May destroyers, corvettes and River class frigates scored the bulk of the warship victories with a few by sloops.

 

[Shortround6]

Much better radar, much better asdic, a far superior ASW weapon in the Squid,

Many of the Japanese escorts or even fleet destroyers did not have radar in the early part of the Pacific war which was more than a bit late by European standards.

The Japanese asdic was several generations behind the British and the gap increased. It also did not not help that some of the late Japanese escorts were noisy.

About as advanced as the Japanese got for ahead throwing weapons was a single 80mm army mortar mounted ahead of the Bridge. This arrived late and obviously was not very effective.
While the British Hedgehog showed up in late 1942 poor training delayed it's use for quite a number of months. Crews did not have confidence in it's ablities or proper training in use. There as a lot more too it than point the ship at the suspected area and fire away.

However the Japanese never even got close even in 1945.

A lot of British or American hunter teams used one or more ships to 'fix' the subs (locate and track) and would then use the radio to coach the firing ship into position. The ships own asdic would not point down enough and the target would be lost on the attack runs. If the first run did not work they would often swap and one of the trackers would make an attack run while the first attacker reloaded it's launcher/s while providing asdic support for the new attack ship.

However this also needs practice, training and good voice radios. This was also going into 1944.

The Japanese in late 1941 were behind, well behind, where the RN was in late 1939 as far as ASW.

However in a somewhat similar historical pattern the numerous (by Japanese standards) escorts don't show up until 1944-45, leaving most of the early war work to be done by a few handfuls of converted destroyers, steam torpedo boats and patrol boats. And in 1942 few had radar, not all had Asdic, DC storage was small and so on.
Much of the ASW was done by fleet destroyers "on loan" in the first part of the war as they didn't have enough escort ships.
In April of 1942 the were only two escort groups (this is after all of the early conquests')
The 1st escort group had 10 old destroyers, two torpedo boats and 5 converted gun boats for the Japan to Singapore route.
The 2nd escort group had 4 old destroyers, two torpedo boats and 1 converted gun boat for the Japan to Truk route.

There were a few other odds and sods but obviously they needed fleet destroyers to fill in. And that leads to poor training or team work. The Japanese never had a ASW school. In fact some of their escort commanders (late in the war?) were from the merchant marine academy and not the Naval Academy and we can imagine how well that worked in mixed groups.
The RN was not perfect but the distinction between the regular navy and "wavy navy" was probably the least marked in any navy.

 

[Reluctant Poster]

In his book "Atlantic Escorts" D K Brown lists the following sinkings of U-boats by class

Destroyers
Modern 9
Inter-war A-I 39
Older (WWI) 26
Towns (Ex USN) 8
Hunt 8

Sloops
Black Swan 28
Older Sloops 12

Frigates
River 22
Loch 12
Captain (US DE) 28
Colony
(US built River) 5

Corvettes
Flower 38
Castle 5

The destroyers as a group were very successful accounting for over 1/3 of the total. The inter-war classes (up to the Tribals and Js) had the highest number of kills. When considering that the majority of them were engaged in other duties this really stands out.

The "crap load" of destroyers that were heavy modified were the WWI vintage V and W classes.

I should have stated that these figures are specific to the Atlantic.

 

[Reluctant Poster]

Repeat post

 

[Reluctant Poster]

Each side has 24 warships at the bottom of Ironbottom Sound.

The chief problem for the IJN is that they could ill afford to lose so many ships, given their limited shipbuilding capacity.

Actual the Japanese have only have 16 warships at the bottom. The others were merchant vessels which A were not warships and B were deliberately beached to unload as the Japanese had no port. They were bombed on land.
Here are the loses of warships in the vicinity of Guadalcanal.

 

[Ovod]

In his book "Atlantic Escorts" D K Brown lists the following sinkings of U-boats by class

Destroyers
Modern 9
Inter-war A-I 39
Older (WWI) 26
Towns (Ex USN) 8
Hunt 8

Sloops
Black Swan 28
Older Sloops 12

Frigates
River 22
Loch 12
Captain (US DE) 28
Colony
(US built River) 5

Corvettes
Flower 38
Castle 5

The destroyers as a group were very successful accounting for over 1/3 of the total. The inter-war classes (up to the Tribals and Js) had the highest number of kills. When considering that the majority of them were engaged in other duties this really stands out.

The "crap load" of destroyers that were heavy modified were the WWI vintage V and W classes.

No mention of the success rate of the escort carriers against U-boats - or does he simply regard carrier kills as aircraft kills?

 

[Reluctant Poster]

No mention of the success rate of the escort carriers against U-boats - or does he simply regard carrier kills as aircraft kills?

Aircraft kills are usually credited to type of aircraft

 

[Alan Stevens]

Actual the Japanese have only have 16 warships at the bottom. The others were merchant vessels which A were not warships and B were deliberately beached to unload as the Japanese had no port. They were bombed on land.
Here are the loses of warships in the vicinity of Guadalcanal.
View attachment 750569

I should have said each side had 24 ships lost at Guadalcanal.

The transports were still valuable ships in the war and the U.S. conduct of the battles were the cause of the Japanese having no port there.

Hiei and Kirishima were upgraded to fast battleships 1937-41.