Attrition by sub?

[Seasick]

If I average sinking at least 1 Japanese cargo/transport/tanker vessel a day will significant attrition occur for the Japanese? If so, where are my best spots to focus on?

[Sardaukar]

Depends if you are playing vs. AI or human.

Against AI one obvious choke point is Makassar Strait.

North of Luzon is good place too. Around Japan are few straits, but mainland Japan can be aggressively patrolled by air units.

[Platoonist]

The Ceram Sea and Bismarck Sea are good hunting grounds once Japan has established itself in the SE Dutch Indies and New Britain. The open ocean between New Britain and Truk is good too, although you have no choke-points to work with there. The AI isn't very good about forming convoys with proper escorts or routing merchants through shallow water like a human player would, so the toll you can take on it is much higher. On the other hand, those dudly US submarine torpedoes.....blah.

[Sardaukar]

British & Dutch subs and USN S-boats have good torpedoes from start.

While USN Mk 14 has spectacular 80% dud rate early war, 60% from Jan 43 and 10% from Sept 43, they still get quite decent amount of ships sunk.

[Trugrit]

If I average sinking at least 1 Japanese cargo/transport/tanker vessel a day will significant attrition occur for the Japanese? If so, where are my best spots to focus on?

30 a month?

Just by sub alone? With or without reliable torpedoes?

I think the question you should ask is:
Are there any players on this forum who have consistently killed
30 Japanese merchant ships a month just with sub attacks?

See if anybody raises their hand.
If they do then ask and follow their advice.

For me the numbers don’t look good in 1942 for sure.
In scenario 1 you get about 70 subs to start the game.

Then in 1942 you get about 40 more but they don’t all come in
At the same time. There are 2 subs that withdraw in 1942.

That is about 108 subs to work with in 1942.
Each one would have to get a little over 3 merchants to get to 365.

In 1943 you get about 75 more added but 10 withdraw.

In 1944,1945 and 46 I don’t know.
I can’t count with my fingers and toes that high.

You are going to have to send them where the Japanese merchant ships go.
Hubs and the straits around Formosa and areas off Japanese ports.
That can be quite a distance.

Hubs are areas of shipping concentration.

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[Nomad]

As an Allied player I consider myself as a moderately aggressive with my subs. In my current game I have sunk 30 ships with sub launched torpedoes in about 15 months. About 2 per month.

[Sardaukar]

By Feb 28 1942, my torpedoes have sunk 76 IJN ships. Versus AI of course.

59 of those have been submarine torpedoes, rest air-dropped.

Not quite one per day by subs, but somewhat 2 per every 3 days.

[Nomad]

The difference between playing against the Ai and a PBEM game. Humans are better at escorting and routing than AndyMacs Scripting.

[RangerJoe]

Early in the war, depending upon how you use your S-boats with working Mark 10 Torpedoes and the Dutch submarines with working torpedoes, then you can get that rate of kills with the American fleet boats chipping in. But once you lose your forward bases, the time spent traveling to and from patrol areas will take a toll on the submarines plus the time deducted from the patrolling. Also and especially against a human opponent, the ASW skills improve both for the air units and surface units.

[Yaab]

And don't forget the war effort at home: one a day into Tampa Bay.

[Seasick]

I recall reading sometime in the past that while during WW1 and WW2 Germany attempted to cripple Britain with their submarine warfare but failed, the US very nearly accomplished that against Japan in WW2. Anyway, sinking shipping capacity has to help.

[RangerJoe]

Actually, Japan was crippled. They had been trying to negotiate a peace treaty through the Soviet Union which would have allowed them to keep their emperor. If I remember correctly, that was their only request towards the end but the Soviets really weren't interested in helping to achieve peace. Which is all that I will say about that.

[Seasick]

By the way, I am thinking about using Dutch Harbor as a forward base for subs vs the AI Japan. I haven't found anything in the manual that says I will need a special HQ nearby. Any comments?

[Platoonist]

By the way, I am thinking about using Dutch Harbor as a forward base for subs vs the AI Japan. I haven't found anything in the manual that says I will need a special HQ nearby. Any comments?

No, you don't need any special HQ arrangements ashore to use a port as a sub base. Ideally, you want plenty of supplies, fuel, naval support and repair facilities nearby if possible. If the port is small, a sub tender might be necessary to get torpedo reloads. I've always used Midway as a forward sub base although it takes a bit of improvement by engineers, an AS and a AR, in port and regular visits by tankers to make it more ideal.

[Sardaukar]

If you want really forward base in north, Adak I. is good (if you can keep enemy from attacking it)...

Midway also works well. And you can send subs that cannot be repaired there easily to PH.

You need AS and AR in base to repair your subs. Ideally ARD too (if your scenario has them, stock has only few).

[Uncivil Engineer]

Here's my 2 cents as someone who has played Japan exclusively in PBEMs.

1 - Palembang provides the vast majority of oil and fuel the Empire needs to function. As the Allies I would saturate either the shallow water east of Palembang or the deeper water of the South China Sea farther east. The typical route out of Palembang is to Singapore or Cam Ranh Bay, then these ships must go through the Luzon or Formosa Strait to get to Japan, but Japan will have better ASW coverage there.

2 - Hokkaido and Sakhalin provide over a third of the resources Japan needs and is very close to Honshu. I would put multiple subs outside Sapporo, Hakodate, Toyohara, and Ominato. China and Manchukuo also provide a lot of resource, but Japan has more options for extracting it. Fusan, Keijo, Port Arthur, Shanghai, and Canton/Hong Kong are all possibilities, with Port Arthur and Shanghai being the most desirable because of quick loading at their large ports and relative proximity to the Home Islands.

[GetAssista]

Here's my 2 cents as someone who has played Japan exclusively in PBEMs.

1 - Palembang provides the vast majority of oil and fuel the Empire needs to function. As the Allies I would saturate either the shallow water east of Palembang or the deeper water of the South China Sea farther east. The typical route out of Palembang is to Singapore or Cam Ranh Bay, then these ships must go through the Luzon or Formosa Strait to get to Japan, but Japan will have better ASW coverage there.

2 - Hokkaido and Sakhalin provide over a third of the resources Japan needs and is very close to Honshu. I would put multiple subs outside Sapporo, Hakodate, Toyohara, and Ominato. China and Manchukuo also provide a lot of resource, but Japan has more options for extracting it. Fusan, Keijo, Port Arthur, Shanghai, and Canton/Hong Kong are all possibilities, with Port Arthur and Shanghai being the most desirable because of quick loading at their large ports and relative proximity to the Home Islands.

Coincidentally those 2 are also the obvious spots to put most (or all) of your early war ASW assets as Japan =)
I usually transfer part of Japan's starting SC fleet to a captured Singapore as soon as possible to catch those brave Dutch/English subs in shallow water around PB, and later put one of the first ASW trained bomber units there. Same for the Hokkaido/Sakhalin area. This concentrated SC/air coverage can be very effective early if Allied subs are brave enough to venture there in numbers