Hōkoku Maru (報國丸) was an armed merchant cruiser of the Imperial Japanese Navy in World War II. She was the name ship of her class. The ship entered service in 1941, and was employed as a commerce raider and submarine tender. She was sunk in a surface action in November 1942.
Hōkoku Maru was laid down at the Tama shipyard in Okayama Prefecture prior to the outbreak of World War II. She was designed as a cargo liner for the Osaka Shosen Lines's regularly scheduled services to South America. Ostensibly a luxury ocean liner, the design boasted a luxury suite of rooms, known as the Nara suite after the city of that name. However the military had a say in the design of Hōkoku Maru, with an eye towards her future use as a troop transport, was built with large government subsidies provided from 1936 onwards.Hōkoku Marus capacity was just under 10,500 gross register tons, with a length of 160.8 m (527 ft 7 in). Powered by two Mitsui B&W diesel engines with 13,000 shp (9,700 kW) driving twin screws, she was capable of 20.9 knots (24.1 mph; 38.7 km/h). She was launched on 5 July 1939 and completed in June 1940.
Hōkoku Maru entered service in July 1940 and made several voyages to Japanese-controlled Manchuria, before being requisitioned in August 1941 for conversion into an armed merchant cruiser. Taken in hand at the Mitsubishi Heavy Industries Yard at Kobe, Hōkoku Maru was equipped with four 15 cm/50 41st Year Type guns, two QF 12 pounder 12 cwt naval guns, two Type 93 13.2-mm machine guns and two twin-mount 533-mm torpedo tubes. In October she was fitted with powerful searchlights and boom for handling a Kawanishi E7K ('Alf') float plane (with one additional aircraft as a spare). Despite her intended role as a commerce raider little attempt was made to disguise her as a simple merchant ship; Hōkoku Marus guns were fitted with gun-shields and were left in open sight, while her paint scheme was a two-tone camouflage design. She was commissioned into the Imperial Japanese Navy on 20 September 1941 under the command of Capt. Aihara Aritaka.
On 15 November Hōkoku Maru, in company with her sister ship Aikoku Maru, sailed for Jaluit in preparation for the opening of hostilities against the United States. On 7 December 1941 the two ships were in the Tuamotu archipelago, at the start of a two-month raiding voyage that sank two Allied merchant ships; SS St Vincent off Pitcairn Island, and SS Malama, near the Cook Islands, before returning to Japan in February 1942.
Following this the ships returned to Japan, where Hōkoku Maru underwent a refit, and was re-armed with 8 x 140mm (5.5 inch) guns. She was also outfitted as a submarine tender, in order to support operations by the IJN's 8th submarine flotilla to East Africa.
In May Hōkoku Maru, again in company with Aikoku Maru sailed for Singapore, thence to the Indian Ocean. There they sank the Dutch tanker Genota, south of Diego Suarez, and the British freighter Elysia, south of the Mozambique Channel, before re-arming submarines of the 8th Flotilla off the East coast of Africa.
In July the two raiders captured the New Zealand freighter Hauraki, which was sent back to Singapore under a prize crew. Returning to Singapore Hokoku Maru was re-equipped with two Aichi E13A ('Jake') floatplanes, and an experimental two-tone dazzle camouflage scheme.
In November Hōkoku Maru, again in company with Aikoku Maru, departed Singapore for the Indian Ocean, in what would be her last raiding voyage.
On 7 November Hōkoku Maru and Aikoku Maru passed through the Sunda Strait into the Indian Ocean. Four days later, on 11 November they encountered the Dutch tanker Ondina, escorted by the corvette Bengal, off the Cocos Islands. As Hōkoku Maru engaged, the two ships returned fire, and a shell (probably from Ondina's single 4in gun) hit Hōkoku Maru's starboard torpedo mount, causing an explosion and an uncontrollable fire which spread to the aft magazine. After a series of explosions Hōkoku Maru sank just two hours after the action commenced; 278 of her crew were rescued by Aikoku Maru. Both Ondina and Bengal were able to escape.
- Hackett, Kingsepp
- Conway p215