This was a Japanese undertaking in belated succession to ‘T’ (i) to take the islands of the Banda Sea, and especially the Tanimbar (otherwise Aru) islands group (24/31 July 1942).
These are a group of about 65 islands in the Sulu Sea to the south of western New Guinea, the north-east of Timor and the north of Darwin in Australia. In geographical terms, the north-eastern islands are part of the Lesser Sunda islands group. The Aru and Kai island groups lie to the north-east, and Babar island and Timor to the west. The islands separate the Banda Sea and the Arafura Sea, and their total land area is some 2,100 sq miles (5439 km˛).
The largest of the group is Yamdena, which has a range of thickly forested hills along its east coast, while its west coast is lower. The main town is Saumlaki, located on the island’s southern end.
'T' (ii) was undertaken by Rear Admiral Koichiro Hatakeyama’s 24th Special Base Force, whose men and equipment were transported by the 2nd Attack Force. This latter departed the island of Ambon on 24 July: air cover was provided by floatplanes operating from the seaplane tender Sanyo Maru, and surface cover by the light cruiser Isuzu and torpedo boat Tomozuru.
On 28 July Sanyo Maru arrived at Teluk Sebakor. While no resistance was encountered on Aru, Bakar and Tanimbar islands, the first landing on Kai island was repulsed by the island’s small Dutch garrison. At 08.00 on 28 July the 2nd Attack Force departed Misool island for Kai island with the minesweeper W-8 carrying one company of the 3rd Yokosuka Special Naval Landing Force and the minesweeper W-16 carrying one platoon of the 24th Special Base Force. The 2nd Attack Force arrived off the Kai islands later in the same day. W-16’s platoon of the 24th Special Base Force and one company of the 3rd Yokosuka Special Naval Landing Force landed by boat, but were repulsed by the local Dutch forces.
At 12.00 on 28 July, the 1st Attack Force departed Babo in Dutch New Guinea for Aru island with the submarine
chaser Fukei Maru No. 15 carrying one platoon of the 24th Special Base Force.
On 29 July elements of Vice Admiral Ibo Takahashi’s 2nd Southern Expeditionary Fleet departed Ambon to begin ‘T’ (ii) proper. The Japanese force comprised the 16th Cruiser Division’s light cruiser Isuzu, the torpedo boats Tomozuru and Syonan Maru No. 1, and seaplane tender Sanyo Maru. The associated Transport Group included the 2,904-ton Manyo Maru and 4,216-ton Hokuyo Maru carrying men of the 24th Special Base Force. With additional reinforcements, the Japanese overran Kai island, Sanyo Maru losing one Mitsubishi F1M ‘Pete’ reconnaissance floatplane to ground fire.
At 15.00 on 29 July the 3rd Attack Force departed Ambon island for Babar and Tanimbar islands with the destroyers Asakaze, Harukaze and Matsukaze of Vice Admiral Densichi Okawachi’s 1st Southern Expeditionary Fleet, as well as the submarine chaser Ch-5 carrying one platoon of the 3rd Yokosuka Special Naval Landing Force.
At 03.10 on 30 July the 3rd Attack Force arrived off Babar island from Ambon island with the submarine chaser Ch-21 carrying one company of the 24th Special Base Force, which rapidly captured the island.
At 04.00 on the same day the 1st Attack Force reached Aru island from Babo on Dutch New Guinea with the submarine chaser Fukei Maru No. 15 carrying one platoon of the 24th Special Base Force. There were only 41 Dutch defenders at the small town of Dodo, and the Japanese captured the island without significant resistance.
At 04.00 on the same day the 2nd Attack Force arrived at Kai island from Misool island with the minesweeper W-8 carrying one company of the 3rd Yokosuka Special Naval Landing Force and the minesweeper W-16 carrying one platoon of the 24th Special Base Force. The Dutch garrison of the island defended itself for a short time, but was soon driven into the jungle, where it continued to fight for another few days before some of its survivors managed to escape by a sailing boat to Australia, while the rest were taken prisoner.
At 04.00 on the same day the 3rd Attack Force arrived at Tanimbar island from Ambon island with the destroyers Asakaze, Harukaze and Matsukaze of the 1st Southern Expeditionary Fleet, as well as the submarine chaser Ch-5 carrying one platoon of the 3rd Yokosuka Special Naval Landing Force. The 13-man Dutch detachment, equipped with two light machine guns, was based in the town of Saumlaki. The Japanese used small boats to get to the jetty, and filed onto this in preparation for a close-order march into Saumlaki. The Dutch detachment then opened fire at close range, and the Japanese retreated to their boats, leaving several dead on the jetty. At 16.00 on 30 July the 1st Attack Force arrived back at Babo from Aru island.
An Australian contingent (‘Plover’ Force of one officer and 29 men) tried to land at Saumlaki island to reinforce the Dutch garrison. The Australian party had departed Darwin on 28 July in the small craft Southern Cross and Chinampa, and while pulling into the jetty at Saumlaki, Chinampa came under fire from the shore: the commander of the Australian detachment was killed, and some of the men were wounded. Both vessels then returned to Darwin, taking the whole of the Australian group with them.
At 04.30 on 31 July the 2nd Attack Force arrived back at Ambon island from Kai island with the minesweeper W-16, and at 09.11 on the same day the 3rd Attack Force arrived back at Ambon island from Babar and Tanimbar island with the submarine chaser Ch-5.