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"Japanese "boat' gun question" Topic

7 Posts

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711 hits since 26 Feb 2019
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Bismarck26 Feb 2019 7:11 a.m. PST

I have seen several references to boat guns used on land against US landing craft and lvts during island landings. So far my Google Fu is weak and I have not been able to find any details, actual nomenclature or descriptions. I am guessing they were modified 37mm antitank guns.

Do any of you WWII buffs know what these were.

thanks in advance,


Ed Mohrmann Supporting Member of TMP26 Feb 2019 8:48 a.m. PST

Sam, the 37mm appears to have been a fairly unsuccessful
(for Naval purposes) Japanese army design.

My guess is the gun you're seeking is the rather
ubiquitous 25mm found in single, twin and triple

However, the 37mm and Vickers 40mm guns (I don't know
if captures/license-built, etc.) are also said to have
been mounted on Daihatsu and used in land combat
by Japanese SNLF and Army units.

More however, the USMC map of Betio defenses

doesn't show any of the 25mm guns but does show artillery
sites of 3 calibers, including the 37mm (smallest).

There is also the type 11 37mm infantry support gun,
designed to be carried by 4 men. Doubt this is the
weapon although it could be since by the time of
Tarawa (Fall, '43) it was obsolete for the Army and
may have found it's way to Naval use. The light carriage
(no wheels) would have also made it useful in arming
landing craft. Its ammunition probably would have been
ineffective versus tanks, but possibly effective versus
early LVT's and, firing HE, somewhat useful versus
MG positions (an original purpose). Not saying this is
the one, though.

The other resource I consulted (
shows no 37mm, but does show 25mm, so I am confused.

Sorry I can't be of more help.

Blutarski26 Feb 2019 1:40 p.m. PST

See the book "Hold the Marianas The Japanese Defense of the Islands" by D Colt Denfeld. In the latter part of the war, the Japanese possessed in respectable numbers a "Model 3 200mm anti-boat gun" (yes, 200mm) described by the author as follows (talking about Saipan):

"Located at the beaches, especially on the more seaward points of land were 200mm anti-boat guns a gun designed to drop plunging fire onto enemy vessels in the bays and inner reef areas."

There is a photo of one of these weapons in the book, showing it dug into an open shoreside emplacement. It is not a large gun something like a very large pedestal-mounted mortar.

Go here PDF link
- for the complete full tilt boogie details on this gun.

Denfeld's book is a GREAT resource, BTW. He has walked the ground and done excellent archival research Very highly recommended.


Bismarck26 Feb 2019 3:21 p.m. PST

Thanks, Byron!

What a beast! I knew they had land emplacements for naval guns, but these were monsters. The PDF is fascinating!
Like Ed responded, my initial query was regarding smaller direct fire weapons that would have targeted Higgins boats and lvts. These things are incredible.
thanks for the info and a great read. Like your Age of Sail game at Southern Front, you are always a great educational resource! :-) Hope you are well and thanks again. Always a pleasure to game and talk with you.


Blutarski26 Feb 2019 7:24 p.m. PST

Hi Sam,
I've got a bunch of data on Japanese WW2 weapons, from infantry arms, artillery, up to coast defense guns. Let me know what you need. I will be happy to put some info together for you.

I'm OK and hope you are as well. Look forward to getting up to the next Southern Front con to run another Age of Sail game or two!

Also agree about that PDF. It is amazing what lurks on the interweb.


Dn Jackson27 Feb 2019 11:01 a.m. PST

Not to hijack the thread…but I remember reading years ago about the 200mm guns. They sound great, but were next to useless. the Japanese packed so much explosive into them that when the shell went off it vaporized the casing. unless they went off very close to the target all the Americans got hit with was a rain of sand.

EJNashIII16 Mar 2019 5:22 p.m. PST

Reading the document it just reinforced the idea that Japan was just so far outclassed. They literally came up with this piece of junk because they didn't have the capability or resources to make something better. Going with get something/ anything rather than have nothing to use.

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