South Pacific:
Flying Boat Tender Akitsushima
by Mike Bennighof, Ph.D.
August 2021

Japanese preparations for a possible attack on Hawaii began as early in 1936, when the Imperial Navy began to look at the potential of long-range flying boats for reconnaissance of the American-held islands and as bombers.

The Kawanishi H6K began very promising trials that year, showing that it could make it to Hawaii and back from some of the coral atolls in the Japanese-held Marshall Islands. In 1938, Kawanishi began development of an even larger flying boat for the Imperial Japanese Navy. This aircraft, which became the H8K, had enormous range and defensive firepower. It did not fly until 1941, when the prototypes showed even greater potential.

Those coral atolls provided sheltered waters; all the seaplane needed was a tender that could provide fuel and ammunition as well as maintenance support. The Navy converted the oiler Kamoi into a seaplane tender, but while the ship could provide fuel and ammunition, it had no repair facilities. The big flying boats needed a dedicated tender.

To give proper support these new and innovative aircraft the Navy requested both a 9,950-ton seaplane carrier and 2,400-ton tender for the flying boats. The big ship still would not have been able to actually carry the huge H8K, and chief naval constructor Keiji Fukuda made a rough sketch of what would be required: a 30,000-ton ship, over 200 meters long. That ship would be larger than any of Japan’s conventional aircraft carriers, and so the Navy settled on the tender approach, enlarging the initial proposal into a 4,600-ton ship.

One ship (to be named Akitsushima) was authorized under the 1939 Naval Program, and a sister ship (to be named Chihaya) in the 1941 War Emergency Program. Akitsushima was laid down in October 1940, launched in July 1941 and commissioned in April 1942. Chihaya was laid down in July 1941 on the slipway at Kawasaki Heavy Industries in Kobe just vacated by her sister, but work stopped in the fall of 1942 and she was broken up on the slip. The 1942 War Emergency program included four more sisters, but none were ever laid down.

Akitsushima, also known as the Geisha, also known as Akitsu-Ryu.

Initial plans called for Akitsushima to pull a flying boat requiring service up a sloped stern using a winch. But the H8K weighed 31 tons, making that impractical, and so the ship had a more conventional stern on which was mounted a massive electric crane with a lift capacity of 35 tons.

The crane would lift the flying boat onto the aft deck, which had a cradle to hold either an H6K or H8K. The ship did not have a catapult; the aircraft would land on and take off from the water. The ship could not carry the flying boat, either, without risking damage to the aircraft or difficulties navigating the ship. Instead, it would lift the flying boat aboard for servicing and replace it on the water when finished. In addition to spare parts, repair facilities and mechanics to perform the work, Akitsushima carried aviation fuel, ammunition, bombs of assorted sizes and up to 36 torpedoes for the flying boats.

For her own protection, Akitsushima had four 127mm (5-inch) anti-aircraft guns in twin high-angle mounts and four light anti-aircraft guns. She also had a depth charge thrower and depth charges. She could make at best 19 knots and carried a crew of 545.

Despite having been designed specifically to support long-range reconnaissance missions over Hawaii, Akitsushima did not participate in the Midway operation. She spent a couple of weeks of training in and around Yokosuka, during which she claimed to have sunk an American submarine in the Inland Sea, but no American submarine losses match the date and place (or come close).

In mid-May she escorted a convoy to Saipan, carrying troops for the upcoming invasion of Midway. There she was struck by a dud torpedo from an American submarine, causing the assembly point to move to Guam. Akitsushima separated from the invasion convoy and headed for Rabaul instead, where she supported the 25th Air Squadron’s H6K flying boats and A6M2-N seaplane fighters.

Over the weeks that followed, Akitsushima helped establish the new Japanese airbase on Guadalcanal, using her heavy crane to load and offload construction equipment. She helped escort convoys, and continued to support the flying boat squadron.

Once the Americans landed on Guadalcanal, she cruised the waters near Rabaul to rescue aircrew whose machines could not make it back to their bases due to damage or expended fuel. While on that mission she encountered the Japanese 8th Cruiser Squadron on their way to what became the Battle of Savo Island. The cruiser lookouts did not recognize this ship with the odd profile and even stranger paint job –ash-gray and light-gray stripes, unlike the uniform blue-gray of Japanese warships – and almost opened fire before she provided the proper recognition symbols.

Capt. Haruo Mayuzumi’s ship eventually became a familiar sight to other Japanese crews, picking up the nickname “Geisha” for her “thick coat of makeup,” as an Army officer put it. Her own crew called their little ship Akitsu-Ryu, a play on the dragon (ryu) names of the big Japanese aircraft carriers. Mayuzumi moored his ship only by the bow when in Rabaul’s Simpson Harbor, swinging her to meet high-level bombing raids broadside-on (since the American planes dropped their bombs in strings, this provided a small target profile) and low-level attacked bow- or stern-first (again, to give a narrow profile to torpedoes or skip-bombing runs). A number of near-misses provided welcome fresh fish for the crew, after the bounty had been dedicated in the onboard shrine.

Lifting an H8K "Flying Porcupine" aboard Akitsushima in the Shortland Islands.

Mayuzumi also used his ship’s relatively shallow draft to keep her in waters where American submarine torpedoes could not reach her. This was a dangerous tactic, since the waters around the Solomon Islands were not well-charted, but he got away with his ship unscathed where others were lost. Akitsu-Ryu spent most of her time in Rabaul and at the Japanese seaplane base in the Shortland Islands, as well as serving as a convoy escort. She was a very active ship, and a lucky one was well, facing at least 21 bombing attacks between July and December 1942 with only what Mayuzumi described as “trifling” damage.

In December 1942 Mayuzumi received a promotion and assignment to the Naval General Staff; he would note after the war that not one man had been lost under his command. Under Captain Yoshimi Takao the ship remained a lucky one, surviving still more bombing runs and a submarine attack without consequence.

Akitsushima left the Solomons in June 1943, spending the months that followed split between convoy escort duty and serving as mother ship to flying boats; in the latter role she helped cover the Japanese withdrawal from the Aleutian Islands. She remained under command of the Combined Fleet, mostly as a convoy escort, until her luck finally ran out. While Akitsushima was at the fleet anchorage at Truk in February 1944, American carrier planes struck her three times with bombs, causing extensive damage. She moved to Palau to receive assistance from the fleet’s repair ship Akashi, but American planes sank Akashi and Akitsushima took aboard technicians and tools from the sunken repair ship to temporarily take over her role.

That didn’t last long; Akitsushima needed dockyard repairs and she spent the next several months at Yokosuka and Kobe. In September she returned to service, escorting a troop convoy to Manila. Later that month she was caught in Coron Bay by at least 30 American carrier planes. A bomb hit ignited her aviation gas stores and she sank rapidly with the loss of four officers and 82 seamen.

Akitsushima appears in Second World War at Sea: South Pacific, as a very active little ship with a very fine drawing on her game piece.

You can order South Pacific right here.
Please allow an extra ten weeks for delivery.

Sign up for our newsletter right here. Your info will never be sold or transferred; we'll just use it to update you on new games and new offers.

Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and NASA Journalist in Space finalist, he has published countless books, games and articles on historical subjects. He lives in Birmingham, Alabama with his wife, three children and his dog, Leopold. Leopold is deeply read in the history of barking.

Want to keep Daily Content free of third-party ads? You can send us some love (and cash) through this link right here. You don’t have to, but Leopold would like it if you did.