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"USN WWII Torpedoes" Topic

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501 hits since 18 Apr 2024
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Comments or corrections?

catavar18 Apr 2024 5:36 p.m. PST

I've read that USA early war torpedoes were not very reliable. If so, what's the best way to represent that? Would a simple negative modifier to hit be enough? If yes, for how long?

My understanding is that USN commanders tried to improve torpedo tactics before the end of 1942 and were much more effective by mid 1943.

Any advice appreciated.

Wackmole918 Apr 2024 6:26 p.m. PST


It very complex so I suggest this y tube video

YouTube link

rustymusket18 Apr 2024 6:34 p.m. PST

As I understand it, it was that they did not explode rather than not hit. But you should look into it further. Good luck.

Personal logo Editor in Chief Bill The Editor of TMP Fezian18 Apr 2024 6:48 p.m. PST

I thought it was a depth issue.

Wackmole918 Apr 2024 7:45 p.m. PST

A classic example of the system at work.

hindsTMP Supporting Member of TMP18 Apr 2024 9:43 p.m. PST

There were multiple issues, including IIRC running too deep, and defective exploder design. Wasn't fixed until at least 1943. I also remember that it was the new-design Mark 13, 14, and 15 which had the worst problems, with the older torpedoes having fewer. This implies that early-war, the old 4-pipers in the Asiatic Fleet should be penalized less than ships armed with the newer stuff.

If you don't have books, there is info on-line, such as this: and


advocate19 Apr 2024 3:28 a.m. PST

An issue covered quite well in the novel "Run Silent, Run Deep".

Fitzovich Supporting Member of TMP19 Apr 2024 5:09 a.m. PST

From my understanding US torpedoes didn't improve until sometime in 1944 and using a negative "To Hit" modifier is likely the best course. I also understand that German torpedoes were below average in hitting, UK, Italian about average and the Japanese were above average.

The interwar period included a world wide economic depression that affected budgets and torpedoes were very expensive items, hence they didn't really get tested under realistic conditions in many cases.

Under the best of circumstances torpedoes are difficult to score a hit with, but when they do the results are likely devastating.

79thPA Supporting Member of TMP19 Apr 2024 6:41 a.m. PST

You could manage it as a hit issue of you want, assuming that a hit only counts for torpedoes that actually detonated. You could also manage it by not giving a negative modifier to hit but, rather, require a roll after the hot to see if the torpedoe/s detonated.

Eclectic Wave19 Apr 2024 10:38 a.m. PST

Don't forget the problem of run away torpedoes. A run away torpedo is one in which the rudder get's stuck and the torpedo does a large circle… coming back to it's starting point.

And yes, there are recorded instances submarines sunk by their own torpedo's.

That's a little bit more then a minus on the to hit die.

ScottWashburn Sponsoring Member of TMP19 Apr 2024 12:57 p.m. PST

The Great Torpedo Scandal was a real travesty. The sub skippers realized very quickly that the torpedoes weren't working properly, but the higher ups adamantly refused to believe it. They would not even permit any tests to be run. When they finally relented they discovered the torpedoes were running much deeper than they were supposed to. Once that problem was fixed there was another battle to convince them the magnetic exploders weren't working right either. Some skippers disconnected them on their own initiative (and were severely reprimanded if they were found out). As noted above it wasn't until well into 1943 that the US submariners got a reliable weapon.

Mark 1 Supporting Member of TMP19 Apr 2024 1:38 p.m. PST

Understanding the failures of USN torpedoes is a case of pealing the onion. There were several failings, each hiding the next one.

In no particular order:
1) The "magnetic pistol" device was intended to detonate the torpedo based on the magnetic field of the target vessel. The idea was to run the torp just below the hull, and detonate directly below to break the vessel's back -- causing irrecoverable damage. However they often detonated early, due to the inconsistent nature of magnetic fields. Launching a torp and having it detonate halfway to the target is a notable failure.

2) The gyros for off-angle firing did not perform consistently. There were notable cases of torps being launched at some off-bow angle (let's say, for example, that the aim point was 15deg to starboard of the bow of the sub). Due to failures in the gyro angling management system the torp would turn to starboard, and CONTINUE turning past the 15deg angle, eventually running a full circle. There were multiple cases of subs observing their own torps coming back to put them at risk, and some cases of subs lost with all hands when there it is suspected that they were sunk by their own torp.

3) The impact pistol was not reliable at all angles. After the submariners concluded the magnetic pistols were a problem, some (even when not authorized) began replacing them with impact pistols. But it was found that the older impact pistols, when striking at hard angles (around 90deg), had a tendency to be crushed BEFORE detonation. The impact pistols really needed to strike at an angle that was 75 or 60 degrees to reliably detonate.

4) The torps ran deep. Even if the gyros and detonators were resolved, the torps ran deeper than set. This was, in the end, due to Naval Ordnance mis-testing, where they didn't want to spend the funds to fire live torps (with warheads), so their testing was without warheads. And a torp without a warhead, weighing so much less, ran more shallow than one with a warhead.

So saying "well, what was wrong?" is a question that begs several answers. And how to account for the failures of USN torps might vary depending on the abstractions of the specific rules (ie: do they track strike vs. detonation separately? Do they track where the miss goes and does it strike another ship? Is there a saving role on damage? etc.). All of these might suggest different ways that USN torp problems might be accounted for.

And BTW other nations had some similar problems. Early German torps, for example, had similar problems with magnetic pistols. But it was much easier, and faster, to get working torps when you face only one failure mechanism vs. when you have several that are stacked up.

Or so I've read. Wasn't there myself.

(aka: Mk 1)

troopwo Supporting Member of TMP20 Apr 2024 7:46 a.m. PST

Mark 1 covers most of it.
The problems were concentrated in the then new Mk14 torpedo used by subs.

They ran too deep.
The ones they tested actually didn't have a weight to simulate the explosive weight if you can believe it. they did this to save money to help recover the test torpedoes. Consequently, the depth settings were usually off by ten to fifteen feet.

The magnetic influence fuses were as problematic as the Germans found in theirs. They ran great in the test areas where they were set for magnetically. However, when you travel the earth, the magnetic anomolies change incredibly and no one accounted for this. Hence, massive failure rate.

The contact fuses did not go off unless the angle was something incredibly small like like 15 degrees off track or less. Meaning anything like a good solid hit at 90 degree angle would not set off the contact fuse. There were cases of Mars being hit by as many as three torpedoes spearing into their hull and sailing away safely. this one was confirmed by the navy when Adm lockwood, the sub commander at Pearl ordered a trial run and had a sub fire live torpedoes into a cliff face in Hawaii.

It took nearly a year for all these things to get worked out and then the Mk14 was very relaible after they worked through all these things. But, that first year there were an incredible number of sub captains that were pretty bitter at their lost opportunities from the first year of the war.

hindsTMP Supporting Member of TMP23 May 2024 9:30 a.m. PST


Based on sources I've seen, I would take issue with a few of the comments you make above, so our fellow TMPers might want to also check out the 2 links I posted earlier.

For example, Crenshaw in his books "Tassafaronga" and "South Pacific Destroyer" refers to similar issues with the Mk 15 destroyer torpedoes (which shared most design elements with the Mk 14), and this is typically more of interest to us miniatures gamers than the Mk 14.


Personal logo foxbat Supporting Member of TMP17 Jun 2024 2:34 a.m. PST

Just for the sake of a a wargaming scenario : what would be your assessment of the problem status, would it have been fixed or given a partial solution by the time of the Empress Augusta Bay battle in November 1943?
Thanks in advance

ScottWashburn Sponsoring Member of TMP23 Jun 2024 3:49 p.m. PST

The best account I have found of the torpedo problems and their eventual correction is in Clay Blair's "Silent Victory".

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