SWWAS: Cruiser Submarines
By Steve Cabral
August 2013

Introduced by Germany in World War I, the cruiser submarine was designed to displace 3,000 tons and usually armed with two 5.9-inch cannon as deck guns. After the Armistice in 1918, the Allied Powers were interested in acquiring U-boats for study, particularly the cruiser types. Several went on to build their own after the Great War. See “French Leviathan” by William Sariego in Daily Content for history of the most powerful cruiser sub: Surcouf. Ironically the German naval staff came to the conclusion the cruiser sub gave too little bang for the buck and the World War II Germans would mass-produce the small Type VII U-boat. First into the cruiser sub sweepstakes were the British, who ordered 12 cruiser subs. These were armed with four 5.2-inch guns in twin-turrets fore and aft on the main deck. The first was the X-1 in 1923. Further studies told the British the cruiser sub was of no value to the Royal Navy; England had the merchant fleet that needed sinking in wartime, not her potential enemies. Further review showed that cruiser subs would be susceptible to ramming as frequently happened to her subs in WW I from operating in close conjunction with surface ships. The remaining 11 cruiser subs were canceled and Britain wound down her submarine fleet and trained them to attack surface ships and escort vessels. This would hamper her in WW II, and Britain’s subs archived little for heavy loss except against Italy’s African convoys. X-1 had such poor machinery she was laid up in 1933 and scrapped in ’37.

	Nautilus, Argonaut and Narwhal (from left), in the 1930s.

Second into the cruiser sub design was the United States, which built three cruisers, Argonaut, Narwhal and Nautilus. Argonaut had two 6-inch/53-caliber deck guns, four forward torpedoes with 16 torpedoes and two aft mine launching tubes with 60 mines. The only purpose built minelayer sub in the Navy, Argonaut was commissioned in 1928, and the latter two in 1930. The Narwhal and Nautilus were a slightly shorter but heavier design that had two aft torpedo tubes instead of mines and carried 24 torpedoes and the same gun armament. Argonaut was off Midway on December 7, 1941, and heard gunfire. Believing an invasion was under way, the crew discovered two DDs bombarding the island and twice attempted attack position but failed. She was then converted into a troop transport APS-1 and was mostly involved in landing raiders and agents until her sinking on January 10, 1943. Narwhal and Nautilus each went on several standard war patrols, but primarily the three boats were used for photo recon, raids, civilian rescues and supply missions rather than combat.  Notably Nautilus and Argonaut carried the Marines to Makin on August 16, 1942 for a raid. Both surviving subs were ordered to Philadelphia in January 1945 and scrapped by May.

The last cruiser subs were the three STO class boats Japan built in 1944-45. They were the largest subs built until the nuclear subs of a generation later. Japan had been heavily influenced by the cruiser designs and many of her I-class fleet boats had a 5.5-inch/40-caliber gun on deck, sometimes two. However many of the one gun designs had a hanger and floatplane aboard; none were in the 3,000t range to qualify as cruisers. Forty-seven Japanese navy subs carried one or more floatplanes aboard. In 1944 the AM class (I-13, I-14) was designed with two aircraft but only 2,620 tons. They were designed first as headquarter submarines but later designated as scouts for the STO class; two were completed. The STO class, also known as I-400 class, displaced 3,500t/6,300t with full load; three were completed. Armed with three float bombers, one 5.5-inch gun aft and six forward torpedo tubes, the vessel was originally designed to launch attacks on the Panama Canal. All three were captured at war’s end and scuttled eventually. However, Submarine Squadron One (I-13, I-14, I-400, I-401) was issued orders for Operation PX, an attack upon the United States in which rats and insects from secret Mongolian labs would be released with cholera, bubonic plague, dengue fever and typhus. The operation was canceled as inhumane by Gen. Y. Umezu, the army chief of staff. Instead, full-scale lock models were built, and after a torturous fuel oil expedition the subs trained their pilots on the Panama attack. Just as they were to set sail in June 1945 the naval staff changed the operation to an attack on Ulithi Atoll. The two scout subs set sail for bypassed Truk with Myrt recon planes aboard and lost I-13 along the way. The two STO boats set sail July 23 for Ulithi but were recalled after the surrender as they had not yet attacked. I-402 was converted from carrier-sub to unarmed fuel transport and saw little war usage.

Using Cruisers in SWWAS

In addition to their function as surface ships, all cruisers may dive and move as submarines (move 1 zone on even turns). If contacted on the surface, cruiser subs start four hexes away from the enemy in daylight, two hexes in Day squall, storm or clear night, one hex in night rain, squall or storm condition (hard to spot subs) on the Tactical Map. Subs never spotted in gales. Most subs submerged in bad weather, calm below the surface. They may forego firing for one round to submerge, but may be shot at that round. Thereafter they are submerged and revert to normal ASW process (16.4). All cruiser subs are limited to gun range of 2 hexes; only Surcouf has gunnery spotting plane to get extended range. A cruiser sub with hull or torpedo damage may not dive. The larger guns on American/Japanese subs are rated as tertiary because they are non-turreted, local control with limited ammo and rate of fire. Surcouf had an actual big ship type turret installed with magazine and lifts. X-1 was designed to fight destroyers even-up.

U.S. cruisers are available in Leyte Gulf scenarios (1944 only). Roll 1D6 each for subs Narwhal and Nautilus and add to a scenario on a roll of one. The Japanese player then picks three coastal sea zones either on or adjacent to a port or airfield the sub may visit. (never Japan, Asia or a facility-less island). The U.S. chooses one sea zone from these and conducts a photo recon (two consecutive daylight turns duration) or landing mission (two consecutive night turns duration). Photo is only done in a facility hex and landings are adjacent to facilities. The hex chosen by U.S. may be the same or adjacent zone to one picked by Japanese navy player. This may be liberally picked, i.e. a sea zone between two facilities would allow that hex, the facilities or either blank zone on either side to be chosen. Allied player gets 1 VP for completing a mission.

Argonaut could be added to any SOPAC scenarios as a minelayer. Roll 2D6 for a 12 in any scenario except those in July-September 1942; costs 1 VP.

Operational Scenario Seventeen
Reaping The Whirlwind
Additional Forces

Allied Reinforcements

Tinian Atomic Delivery
Turn 122
At Tinian AY 82
CA-35 Indianapolis

Axis Reinforcements
Turn 64
At Kure (K 84)
Flotilla 5: 2 x I-boats (I-58. I-53)

Turn 100
At sea (H 107)
Submarine Squadron One
I-400
I-401

Turn 120
At Truk (BO 87)
Flotilla 6: 1 x I boat (I-14)
1 x A6M5
1 x G4M3
1 x C6N1

Special Rules

11. CA-35 must exit map west edge north of Ulithi by turn 137. The Allied player receives 2 VP if successful.

12. Submarine Squadron One must get within four hexes of Ulithi and spend one turn on surface launching an attack. If successful receive 1 VP per sub (I-400 or I-401) launching an attack. May not attack before Myrt C6N1 completes recon and must be a ship in harbor to attack. They may sail as a Raid TF or as normal subs. Flotilla 6 is free for normal sub operations after arrival.

13. Use any marker for C6N1. It must fly over Ulithi and return to Truk. The weather must be clear on turn over Ulithi. It takes two turns to reach Ulithi from Truk. 24/4 is speed/endurance; it may not be intercepted.

The USS Indianapolis was sunk by I-58 en route to Leyte after delivering atom bomb components to Tinian 7/30/45 with a loss of 883 lives. The I-400 subs sailed toward Ulithi in two separate Flotilla’s and a rendezvous delay allowed the U.S. time to drop the A-bombs on Japan, ending the war before the strike took place.

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