|Operator||Nippon Yusen (NYK)|
|Gross tonnage||3,156 tons|
|Departure date||20 January 1944|
|Destination||Hollandia, New Guinea|
|No. of POWs||611 Indians|
|Location of disaster||East waters of Palau|
|Date of disaster||21 January 1944|
|Photo||Courtesy of NYK Maritime Museum|
Ikoma Maru was transporting 611 POWs (Independent Brigade; the Indian soldiers forcibly incorporated into the Imperial Army, some of whom had worked in the Palau Islands for the past six months), gasoline, provisions, ammunition, and mail, as a member of the convoy consisting of Yasukuni Maru, and escorted by sub-chaser No. 32 and auxiliary sub-chaser No. 47.
In spite of the adverse weather conditions, upon receipt of an Ultra, the USS Seahorse made a long high-speed run for several hours to get in front of the convoy and ambush. At 2317, she made a nigh-surface attack and fired three torpedoes against the near transport (Ikoma Maru), and scored one hit. When the Seahorse was coming around to attack the second ship far away, one of the torpedoes which had missed the first ship unexpectedly hit the second ship (Yasukuni Maru), and she went down to the bottom in 20 minutes.
By the first attack, Ikoma Maru was hit at her port side engine room. By the second attack, a torpedo hit No. 3 hold where gasoline was loaded. She exploded in very bright flames, and sank in a matter of minutes. The two sub-chasers ran around in the rough seas, and picked up the Japanese first, and then the Indians. Forty-three crewmembers and 418 POWs were killed or drowned in this disaster.