Operator	Iino Kaiun (captured ship, former Dutch Toendjoek)
Classification
Gross tonnage	6,200 tons
Speed	12 knots
Departure point	Surabaya, Java Island
Departure date	24 February 1944
Destination	Ambon, Ceram Island
No. of POWs	3,500 (Most of them were the Javanese Romusha (laborers) with 200~300 POWs)
Location of disaster	Off Bali Island (near 07-41S, 115-10E)
Date of disaster	25 February 1944
POW casualties	More than 3,000
POW survivors	Less than 500
Photo

Since the death and sickness rates of POWs forced to work in the Ambon and Haruku areas were so high, it was necessary to replace them with POWs in good shape from Java. On 24 February 1944, approx. 3,500 Romusha and others were gathered in Surabaya to be transported to Ambon aboard Tango Maru. A convoy consisting of Tango Maru and Ryusei Maru (Nakamura Kisen’s cargo ship) left Surabaya with escorting Mine sweeper No. 8, No. 11 and Auxiliary sub-chaser No. 5 Takunan Maru. On this day, two US submarines Raton and Rasher operating in this area received an Ultra and were informed that a two-ship convoy would pass through their patrol area between 1800 and 2000 on 25 February. They steamed through Lombok Strait, and reached a point approx. 20 NM north of Bali Island. At 1730, Rasher sighted the convoy, and decided to turn away to get ahead of the convoy's intended course and contacted Raton by radio to notify his intentions.

The sun had already set, and the faint light and rough seas were perfect conditions for a night-surface attack. At 1943, Rasher fired four torpedoes straight to Tango Maru about 900 meters away. When Rasher pulled away to reload, three torpedoes hit the target and tore her apart. Within five minutes after she was hit, she disappeared under the waves. About 10 minutes later, underwater explosions were heard from the ship's boilers. More than 3,000 Javanese Romusha and POWs were killed.

Ryusei Maru was also sunk by Rasher. Four thousand nine-hundred and ninety-eight crewmen and soldiers were decimated in her sinking. About 8,000 deaths in two successive attacks may have been the highest casualties at sea in history.