Cruel Seas, Profiles

The Imperial Japanese Navy in Cruel Seas

Menaced by PT Boats, the Imperial Japanese Navy needed ways to tip the balance in the Pacific...

The Imperial Japanese Navy in Cruel Seas
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Menaced by the fast-moving PT Boats of the US Navy, the Imperial Japanese Navy found itself on the back foot. They attempted, through various, methods, to tip the odds back in their favour...

Land of the Rising Sun

After centuries of splendid self-imposed isolation, with an obsession that the old Japanese ways were best, Japan transformed itself almost overnight in comparison, into a driven modern and technology-led society. Nowhere else was this to be true than in its magnificent navy that came from nowhere to be the 3rd largest in all the world by 1920, following behind the USA and the largest, Great Britain.

Knowing how backwards their armed forces had become, Japan looked to Europe for inspiration, in particular to France who sold them the notion of the Jeune École ("Young School"), a strategic naval concept which featured small but powerful and fast torpedo boats and light cruisers. And then to a love affair with the Royal Navy who also not only trained them in gunnery and torpedo work but also built them ships as good as their own. By the Russo-Japanese war of 1904, the IJN could field 63 torpedo boats and many other larger vessels. Japan nudged even closer to Britain in WWI, sending torpedo boats and cruisers into the Mediterranean to relieve pressure on an overworked Royal Navy.

The Long Lance

Between the wars Japan reassessed its position with its navy, building the world’s first purpose-built aircraft carrier, the Hosho in 1921 and inventing its deadly fast and powerful type 93 24’’ oxygen fuelled torpedoes. They also decided that as their industrial might could not match that of the west, then they would have to have sharp, training tactics and a crew of superior quality to their foe, and for a while, achieved just this.

A Long Lance torpedo on the beach at Guadalcanal - Imperial Japanese Navy

A Long Lance torpedo on the beach at Guadalcanal

Japan’s lack of escorts, MTBs and small coastal craft allowed the allied submarines to run rampant against firstly the Japanese merchant marine which was eradicated by late 1944, and then the smaller craft and aircraft to tear into the thousands of flimsy, underpowered barges and sampans that the Japanese Army and Navy had to use in a desperate and brave attempt to supply their hundreds of dispersed garrisons spread over tens of thousands of square miles.

In Cruel Seas, you will be gaming the cat and mouse hunts that happened nightly in the Philippines, Guadalcanal and the Solomon’s. They could be IJN sub chasers stalking a crippled US submarine, or mine layers plying their trade at night. Most commonly it will be Japanese barge convoys defending themselves in shallow water against rapacious PT boats. Turning the tables, a late war game could be played out with American landing ships and the terrifying Shin’yo Kamikaze craft.


A typical medium minelayer would be the Itsukushima. She could make 17 knots and carry up to 500 mines! She was also armed with 3 140mm main guns, 2 80mm AA and no doubt multiple 25mm MGs. She served well, downing 4 attacking Mitchell bombers before eventually being sunk by a Dutch submarine.

Itsukushima circa 1935 - Imperial Japanese Navy

Itsukushima circa 1935

Another minelayer, a lighter vessel was the Yaeyama, of 20 knots. The vessel could carry a useful 185 mines with 2 x 120mm guns and 13mm machine guns. Later converted, like many other ships, into a sub chaser, with 36 depth charges, she was overwhelmed and sunk by over 100 US aircraft, the fate of many IJN ships. A few, perhaps five, minelayers were purpose-built, called Fusetsukan. Many more were converted civilian boats, ships and fishing vessels. Minesweepers, always useful craft, were of equivalent size and shape. The IJN built 35 purpose-built ships and used several captured Dutch, British and American ships, whilst over 100 merchant ships were converted to this role.

For anti-submarine work, the Navy built 200 of type 1, of which 81 were lost. These were shallow draught and carried sonar and hydrophones, 36 depth changes, 2 x 40mm gun and an 80mm mortar in the prow.


In an attempt to gain security on the seas, the IJN built over 170 “Kaibokan”, ocean defence ships. They came in four main classes: “Shimushu”, “Etorofu”, “Mikura” and “Ukura”. The classes did vary but typically were capable of twenty knots and carried 3 x120mm deck guns with up to 15 25mm a/a, 60 depth changes and an 80mm mortar, used to fire ahead of the boat in submarine hunts. The better-equipped ships packed in more anti-aircraft guns and some had radar. The Ukura, class, of which 29 were built, were particularly tough boats and difficult to sink.

Imperial Japanese Navy escort ship Etorofu in 1943

Imperial Japanese Navy escort ship Etorofu in 1943

Two, larger, ship types were used in the coastal water. The Japanese took old obsolete destroyers and took out some boilers, heavy guns and torpedoes. These became lighter, more seaworthy patrol boats and were also used for landing troops and small landing craft.

Larger tank landing craft T101 class were ordered in number and in design and look, seem to have been modelled on the British TLC of the time. They were welded angular and cheap to build, 90 days from start to finish. When not delivering tanks onto a hostile shore, they were armed with 25mm AA guns and equipped with depth changes and radar, in a manner familiar to the German “F” lighter. A smaller version the T103 class also saw service and would have been poor targets for torpedoes.


Just as Nazi Germany had to reach for desperate solutions toward wars’ end, Japan followed their air force in developing a Kamikaze or suicide weapon that might just turn the tide of the battle. These were the ‘Shin’yo’, or Seaquake speedboats, over 6000 were built after 1943. A one-man power boat with a speed of 30 knots and a massive 700-pound explosive charge, they were to be run at enemy vessels and if a hit scored it would be deadly. The army also built tiny speedboats, the 2-man maru-no which carried 2 depth charges as its main weapon. Mainly used in the Philippines, they were organized into sea raiding regiments, 1, 2, 3,26,27,28 & 29, with 100 boats in each regiment.

They fought bravely in numerous actions but were broadly sunk by aircraft, destroyers, and PT boats. As they were manned they could even turn around and do a second run if they missed their target and had the option of abandoning the craft if possible, rather than suffer certain self-immolation. Fortunately for the allies, the vast majority of the boats were not in the front line but held back in Japan for the proposed final battles. They did cause some severe damage to US destroyers, particularly the large landing craft, several of which were sunk.

A Shin'Yo suicide boat begins its attack run! Imperial Japanese Navy

A Shin'Yo suicide boat begins its attack run... under test conditions with the USN!

Japan, like Italy, Germany and the UK also saw the opportunity for midget submarines, indeed the first actions of the Pacific war at Pearl Harbor was heralded by 4 mini subs attempting to penetrate the Dockyards.

They did little or no damage, but later craft called “Kaiten” “Turning of the heavens”, type 1 and 2, were a different prospect. Not so much as a ship as an insertion of a human being into a very large torpedo”. The one main suicide weapon carried a 3000-pound warhead, deadly as USS Underhill (DE 682) found out when she was sunk by one. Over 100 of this craft were lost with few gains, but when carried on the hull of a large, mother submarine in 1945, they potentially became a more viable clandestine weapon.

The IJN, therefore, is an interesting mixture of the very sophisticated and the very amateur, boldness being a connecting factor whether in battleships or tiny craft. It is a do or die force, get in close and things will go well, dither or maintain the range of the allied technology and firepower will overreach you.

The Imperial Japanese Navy in Cruel Seas

The Imperial Japanese Navy Fleet box set Contains:

  • 6 x T-14-class MTBs (metal)
  • 3 x Maru-Ni kamikaze boats (metal)
  • 3 x Shin-Yo kamikaze boats (metal)
  • 4 x large Sampan (resin and metal - two of each canopied boat)
  • 1 x Escort Type Hei minesweeper (resin & metal)
  • 1 x Aichi D3A 'Val' (metal)
  • Ship Cards
  • Plastic Torpedo markers

Imperial Japanese Navy Fleet

View in Store

Close Quarters

Within the pages of the Close Quarters Supplement for Cruel Seas, you'll find additional ship rosters for both the Imperial Japanese Navy and Imperial Japanese Army, as well as three additional historical scenarios centered on the Pacific Theatre.

Additional Vessels

Tom Mecredy
Tom spends most of his time buying books and painting miniatures. He enjoys putting animals on the bases of his miniatures and half-finishing side projects. Some say that he lives in a tower on top of some windswept northern hill with his wife and cow-patterned cat, Spaghetti.