Japanese seaplane tender Akitsushima

Akitsushima (秋津洲) was a seaplane tender of the Imperial Japanese Navy (IJN), serving during World War II from 1942 until being sunk in September 1944.

Design
In 1938, the IJN wanted to use their large-sized flying boats more effectively, because the Kawanishi H6K was the only aircraft able to hit Pearl Harbor directly from the Marshall Islands. However, the Marshall Islands did not have flying boat facilities at that time. Early in 1939, the IJN converted the oiler JAPANESE SEAPLANE TENDER Kamoi to a seaplane tender. However, she was not able to repair seaplanes.

The IJN therefore planned two kinds of seaplane tenders which were included in the Maru 4 Programme. One was a 10,000-ton class flying boat carrier, the other a 2,400-ton class flying boat tender. These plans were not able to pass the assessment by the Ministry of Finance. These two basic plans were revived by the Maru 5 Programme in 1941. However, their construction did not begin. Therefore, the IJN planned a 3,500-ton class tender, which was a scaled-up model of the 2,400-ton class. The ships should be able to maintain, repair and supply seaplanes. The IJN intended to accommodate the flying boat by bow-up trim and slope at first, however this plan was cancelled and the Akitsushima class was equipped with a 35-ton crane. The IJN changed the design frequently, ending up with a displacement increased by 1,000 tons.

Operational service
While running sea trials off Wadamisaki, Kobe, Japan, on 21 April 1942 in the aftermath of the Doolittle Raid — which had taken place on 18 April — Akitsushima opened fire on an approaching Japanese transport plane her crew mistook for a United States Army Air Forces B-25 Mitchell medium bomber. Splinters from Akitsushima′s anti-aircraft shells struck the nearby Japanese passenger ship Tennyo Maru, prompting  Tennyo Maru to transmit a mistaken report that the plane had attacked her with machine-gun fire.

Akitsushima was commissioned on 29 April 1942 and assigned to the 25th Air Flotilla, 11th Air Fleet. Two weeks later, she sailed to Saipan and Rabaul. After the U.S. invasion of Guadalcanal, Akitsushima arrived at the Shortland Islands on 16 August 1942. She was damaged by B-17E Flying Fortress bombers at Buka Island two weeks later.

Her repairs were completed on 5 January 1943, and she was dispatched to Kavieng, only to proceed to Jaluit Atoll in February. On 30 June 1943 she sailed to Paramushir for the evacuation of Kiska. She returned to Yokosuka in August and sailed via Shanghai to Truk. Here, she was slightly damaged by U.S. carrier planes which attacked Truk during Operation Hailstone. The following month, Akitsushima was assigned to the 14th Air Fleet and returned to Yokosuka for repairs. She also received repair ship facilities, because the repair ship JAPANESE REPAIR SHIP Akashi had been sunk. Her refit was completed on 1 August 1944 and she was assigned to the 2nd Fleet.

In August 1944, she sailed to Kure and Imari, then to Kaohsiung and Manila, finally arriving at Coron Bay on 23 September 1944. Here she was sunk by aircraft of Task Force 38 the following day. Akitsushima was officially struck from the Naval register on 10 November 1944.