Ok, if we are going to tweak things to get a more realistic and historical I thought it might be useful to compare and contrast ASW doctrine and development between the IJN and the Allies (RN, RCN and USN).

Here are two links to start:

http://uboat.net/allies/

http://www.combinedfleet.com/

REPORTS OF THE U.S. NAVAL TECHNICAL MISSION TO JAPAN

http://www.fischer-tropsch.org/prima...USNTMJ_toc.htm

We could look at:

1) Pre-war ASW doctrine

2) Wartime experience and development

3) Technology and weaponary

Just to start. Please add in your 2 cents.

Japanese ASW weapons and stats

http://www.navweaps.com/Weapons/WAMJAP_ASW.htm

Japanese radar

http://www.combinedfleet.com/radar.htm

Japanese Sonar and ASDIC

http://www.fischer-tropsch.org/prima...ort%20E-10.pdf

I forgot the sight, but I remember reading the actual patrol reports from the different fleet subs in the Pacific. I think that would be invaluable.

American Sub Doctrine at the start of WW2 in the
pacific was to protect the BB TFs and sink enemy warships (same as Japans). Adm Nimitz changed all that when he
figured that Japan, like England, was an island nation and needed to ship in all the resources to sustain itself. So he
used the German approach to go after the merchant & tanker ships (or convoys later) doing the resupply. I think that
caught Japan off-guard in relation to what American Subs would be doing till at least late in 1942 when they finally
started to catch on....

JIM

Stickied!

As you can see from the IJN ASW link, they had no real doctrine at all, frankly. Not in relation to merchant shipping in particular.

It's important to remember that DCs are, um, explosives, and they sit on the deck, unprotected. For a ship that saw its role as using them as offensive weapons against their submarine foe, they are critically important, and ready for quick use. For a navy whose doctrine was that DDs were offensive platforms with capital ships as the foe, not submarines, DCs on the deck are unarmored bombs waiting to be detonated by just about anything heading their way.

For a feeling of IJN ASW doctrine, I really suggest buying The Japanese Merchant Marine in World War II by Mark Parillo. Unfortunately it is out of print. He goes into great detail regarding the timeline of IJN ASW activities.

Thanks Tater, I've spent some time this evening searching for info on IJN anti-sub detection devices. Nothing on sonar or hydrophones or their capabilites, nor how they compared to Allied ones. :-?

I got info on radar, that's a start, we need to find out more about ASW air support or lack of it.

some thoughts:

The IJN never developped an effective radar, but IJN crews were trained in night fighting and had superior binoculars and optics to the allies. In 1942 around Guadalcanal, there were many instances when IJN crews would spot allied surface ships at night 3-5 minutes before the japanese ships showed up on US radar.

IJN crews were very highly trained at the beginning of the war and this gradually tailed off as replacement and green crews came in. At the beginning of the war, there were many instances where US subs would attack a convoy or warship only to then be subject to a ferocious counterattack from IJN fleet destroyers.

However, the IJN never developped an effective ASW doctrine since they viewed ASW work as being "defensive" and beneath them. Therefore there were many flaws in their attack doctrine, they tended to set their depth charges at shallow setting (100 feet I believe), since they thought allied subs could not go much deeper. They also broke off depth charge attacks sooner than allied escorts, allowing many allied subs to escape.

As the losses mounted, Japan instituted a proper convoy system at the end of 1943, but never with the same level of dedication as the allies.

I have a couple of reference books at home if you are looking for specific info. WW2 naval actions in the pacific has always been one of my area of interest. I'll see what I have on IJN sonar and depth charges.

The IJNAF would have used various seaplane units to provide air cover over island bases. This would be usually a Mavis (H6K) unit. These planes should be spotted as singletons. They might bomb and report. Meanwhile (early in the war) there would be little forthcoming in terms of air attack. Hunting subs is not like hunting a CV battle group. The sub is either destroyed in the bombing, or it dives, and the added aircraft are a wasted effort.

So in a realistic H6K radius around a jap island, have a chance of a Mavis attack. Later there might be other floats (CA floats, notably). G4Ms (Betty) might also get tasked for this role sometimes as well, maybe G3Ms (Nell) as well. Seeign fighters anywhere but very close to land seems wrong, they would not have been used, it would be more of a random encounter for the fighters... "there we were, when we looked down and saw a sub. I made a hand signal to my chutai, and we strafed until the sub dived, then RTBed."

The air side of SH4 is pretty silly right now, frankly.

The IJNAF also did not have VS units as part of CV air wings. They had VB, VT, and VFs. They'd obviously likely fly some ASW patrols, but it would have to be with Kates or Vals since most Zeros didn't have radios. Regardless, I'd expect to almost always see any non-maritime patrol aircraft in 3s snce the fundamental unit of japanese aircraft organization was the 3-plane Chutai.

On a slightly related note, the IJN CVs need a mod to remove the aircraft from the flight deck. IJN doctrine had all aircraft embarked below in the hanger spaces. PLanes were fueled, amred, and warmed up below decks (mostly). This allowed the flight deck to be clear for CAP take off and landing ops. This is the opposite of USN doctrine which embarked all aircraft on deck, and only struck them below for maintenance. USN CVs should have all the planes forward (jam-packed), or all the planes aft (also jam packed). So the IJN CVs would look more realistic without planes on deck unless you happen to be shooting while they are about to launch a strike (in which case it should be steaming into the wind at flank speed).

Back to escorts, I think it will be a tough task to find good info on their doctrine regarding the prosecution of submarine contacts. It's easier to look at the general scheme of things instead. In terms of mods, this would mean making the escorts act a little more like USN/RN DD/DEs (notably minus radar) , but reducing the number of such escorts. It is plain from Parillo's book, as well as Evans and Peatie's excellent book, Kaigun, that until 1943, there was zero attention to the submarine issue at all. There were literally 2 officers in the entire fleet tasked with escort organization, and that was in addition to other stuff on their plates. 2 part-time officers to conduct all navy organization regarding escort activity. Otherwise, escort duty was the bailiwick of the regional admirals. Taking DDs away from the Combined Fleet was not looked upon well.

Also, while not strictly an ASW issue, the japanese subsidized a "scrap and rebuild" policy of the merchant marine. This required 4000 ton ships that could make 13.5 knots. Many such ships were built. As a result, the merchant captains were against convoys themselves since moving at the speed of the slowest would often result in a group of 13.5 knot ships having to wait for a single slowpoke. Independant shipping was the result. Actually, another factor came into play there. the japanese couldn't offload ships very efficiently. So a convoy would saturate a port's ability to deal with the cargo. So cargo carriers tended to like showing up, unloading, then leaving without having to wait. They needed to, too. The japanese required more shipping than they actually had, it needed to be at sea as often as possible.

From the SH4 standpoint, I think that the radar needs fixing, the uber-intel of units radioed to the player needs to radically drop, and subs need to be forced to patrol around mostly for isolated ships. Note that in the main sea lanes (Japan-Truk, Japan-Singapore, and to a lesser extent Japan-Palau) the IJN would patrol. Not escort usually (before '44), but patrol.

It seems the IJN did have operational (and effective) radar from 1943 on, but it was inferior to US radar.
Generally it seems to me the IJN became gradually more effective in ASW during WW2, but could not capitalize on this experience in 1944 because of the general slaughter that ensued on land and in carrier battles.
Similarly to the italians, who totally bungled ASW in 1940/41 but got quite good at it in 1943.
Keep in mind most USN subs were lost in 43/44, and losses to planes only started in 1944/45 when the IJN apparently had airplane based radar.
Sadly SH4 has totally useless river gunboats, but no Ukuru class escort ship or Tomozuru class torpedo boat.


Regarding the CVs, the regular scouting duty done by VS squadrons in the USN was done by the carrier attack planes in the IJN. The Aichi D3A (Val) dive bomber was awkward to handle on carriers since it had non folding wings. The B5N (Kate) torpedo bomber had better range, DF equipment and a third crewmember to help with navigation. At least on approach to midway, one carrier always had flying duty comprised of attack planes on ASW patrol.

Really interesting...

http://www.navweaps.com/Weapons/WAMJAP_ASW.htm

Allied the most used allied Depth Charge was the 420lbs. one, with a lethal radius between 4.3 filled TNT in early and middle war times, and 7m filled with Amatol/Minol in later war times.

Japanese only has 220lbs, Depth Charges with a rate of sink of 1.9m/s.
This means the lthal radios must to be much samaller than above for 420lbs.
Sure they needs to explode so near the hull, almos the half of the above values for 420lbs, may be between 2m and 2.5m.

Only after 1943, japanese developed a 357lbs, Depth Charge, with a rate of sink of 3m/s.
The lethal radius for them must be between 3m and 4m only.

Ingame defalut settings are a random value between 4.5m and 40m.... a very unrealistic value...

I changed the lethal radius to a more moderated values, now i am using a random value between 4.5m and 10m, wich is too biger than in real life.

4.5m is about the double of the real life value, and 10m is about 4 times the real life value.

Plus i reduce the sink rate from 5m/s default down to 3m/s wich is near 60% more higher than in real life (1,9m/s)

It is similar i done for SH3, works fine.

Added the giant USN technical report on Japanese Weapons from 1945 , including a link to Japanese sonar. :up:

Radar - based on my reading, Samuel Morison's History of U.S. naval operations in ww2 and Clay Blair's Silent Victory, IJN ships never carried an effective radar, certainly not one that ever had any practical effect in any battle, does anyone one have solid evidence to the contrary?

Depth Charges - as Redwine pointed out, the IJN never developped heavy depth charges like the allies.

ASW capabilities - If you read through the documented encounters between the IJN and U.S. subs troughout the war, the IJN was at it's most effective at the beginning of the war. All their destroyers were equipped with sonar and they knew how to use it. However, from my reading it appears they never developped the team tactics used by allied escort, rather each escort would attack on its own. The IJN ASW effort became progressively worse as the war wore on and the crews became greener.

U.S. intel - The U.S. Navy broke the japanese codes before the war and were reading japanese messages throughout the war. They kept close track of the movements of japanese ships and U.S. subs were often dispatched to intercept specific warships or convoys, so the superb intel we get in SH4 is based on fact, although it may require some tweaking.

RDF - The japanese had a very effective Radio Detection Finding network set up before the war which allowed them to keep close tab on allied warships. The U.S. knew this from intercepted messages, which is why U.S. subs used their radios sparingly, although I don't know how this could be integrated in the game.

One, Samuel Eliot Morison is a good overview, but it's the USN take on things from right after the war. Little or no japanese sourcing. That said, the IJN did have some effective radars later in the war, but there were bloody few of them. Convoy escorts (usually NOT fleet DDs) just didn't get such gear.


While true, the problem is that the escorts in question were virtually always escorting other warships, or merchants that were part of an invasion fleet. They knew how to use the tools they had, but they had no operational doctrine for ASW at all, really. No overall plan. Interestingly, their fleet CAP was similar. Throw some Zeros up, and they'd fly around looking for AAA fire to alert them to contacts (since few carried radios) and hunted on their own. This is in stark contrast to radar tracked, CIC tasked CAP in the USN.

[quote]U.S. intel - The U.S. Navy broke the japanese codes before the war and were reading japanese messages throughout the war. They kept close track of the movements of japanese ships and U.S. subs were often dispatched to intercept specific warships or convoys, so the superb intel we get in SH4 is based on fact, although it may require some tweaking.[quote]

Quite true, though depending on the year the number of convoys may be too high IMO.

Excellent point. Does sending a contact report attract attention? Any IJN warships should be alerted by their sigint section...

tater

I was looking through the japanese ASW section of the report of the U.S. naval technical mission to Japan that JOEA linked to:

http://www.fischer-tropsch.org/prima...ort%20S-24.pdf

it seems to contain all the info we need on IJN ASW capabilities and tactics to properly tweak the game.

I'm not sure how much info can be gleaned/reverse engineered from the reports about the sinkings of US subs, but this site (http://www.csp.navy.mil/) has what seems to be some really good info about all of the US subs lost in WWII. I've just started playing around with stuff there, but it was interesting to learn that of the 25 US submarines lost through the end of 1943, 11 appear to have been lost to enemy surface ships and only 3 to enemy air attack (and one of those was while in port, though another 3 are attributed to mines but could possibly have been unreported air attacks), with 6 or 7 having been losts in accidents and 1 to an enemy sub. In terms of what sort of results to aim for in tweaking, it would seem that surface vessels should be about 2-4 times more dangerous than airplanes, at least during the first couple of years of the war.