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  RO-33 Japanese Submarine
Kaichu Type submarine

1,109 Tons (surfaced)
264' x 23' x 13'
4 x forward torpedo tubes
10 Long Lance torpedoes
1 x 80mm gun
2 x 25mm guns

Click For Enlargement
IJN 1942
Sub History
Built at the Kure Navy Yard in Kure. Completed October 7, 1935. Commissioned into the Maizuru Naval District. Assigned to SubRon 4 in SubDiv 21, commanded by LtCdr Sakamoto Eiichi.

Wartime History
At the start of the Pacific War on December 8, 1941, this sub participated in Operation "E" the Invasion of Malaya. Departs Sasebo with RO-34 and the Maki Unit to raid enemy forces off Malaya and Java.

On February 15, 1942 RO-33, I-53 and I-55 are ordered to intercept cruisers HMS Exeter (68) and HMAS Hobart (D63) but the submarines were unable to locate the warships. On February 20, 1942 transited Lombok Strait into the Indian Ocean. Between March 1, 1942 to March 4, 1942 patrolled off Tjilatjap and spots several enemy transports and destroyers and attempts to attack but fails to score any hits.

On March 10, 1942 SubRon 4 is disbanded and RO-33 and RO-34 are assigned to SubRon 6 under the command of Vice Admiral Inoue Shigeyoshi, 4th Fleet patrolling Palau and Truk. On April 4, 1942 both RO-33 and RO-34 were assigned to the South Seas Unit. On April 15, 1942 departs Truk and three days later arrives in Simpson Harbor off Rabaul and was placed under the command of LtCdr Kuriyama Shigeshi.

On April 20, 1942 departs Rabaul to reconnoiter Port Moresby and search the Jomard Passage for convoy routes and to reconnoiter Deboyne Islands and the Rossel Island for suitable anchorages before to the planned operation against Port Moresby. Afterwards, RO-33 and RO-34 are ordered to blockade Port Moresby and help guide Japanese ships into the area. On April 23, 1942 returns to Rabaul.

On 1 May 1942, departs Rabaul as part of Operation "MO" to the Jomard Passage in the Louisiade Archipelago with DesRon 6 including light cruiser Yubari, four destroyers and a patrol boat escorting a force of twelve transports and a minesweeper.

On May 5, 1942, RO-33 arrives off Port Moresby and on May 10, 1942 departs for Truk. On May 23, 1942 departs Truk with RO-34 bound for Japan. On May 30, 1942 arrives Sasebo for overhaul and repair and departs on July 9, 1942 with RO-34 and returns to Truk on July 17, 1942. Six days later departs for Rabaul with RO-34. On July 29, 1942 departs Rabaul bound for the Coral Sea and off Port Moresby and the southeast coast of New Guinea.

On August 6, 1942 RO-33 was north of Murray Island in the Torres Strait Islands of Queensland then proceeded into the Gulf of Papua. At 10:34am, spotted and chased MV Mamutu and around 11:00am opens fire with the e 80mm deck gun and scores repeated hits, sinking the vessel with great loss of life and only 28 survivors. Wartime accounts claim RO-33's captain Kuriyama ordered his crew to machine gun the survivors. Yet, the account of the sole survivor and Japanese sources dispute this claim, stating the submarine only used the deck gun.

On August 7, 1942 RO-33 was ordered to patrol Indispensable Strait and reconnoiter the U.S. landing on Guadalcanal then make contact with Japanese forces ashore. On August 11, 1942 arrives off Lunga Point. On August 12, 1942 arrived off Cape Hunter and contacts Japanese forces ashore and learns from them an enemy task force consisting of two carriers, two battleships, five cruisers and several transports were observed leaving Guadalcanal and LtCdr Kuriyama relays this information to headquarters. On August 13, 1942 delivers food to Japanese forces on Cape Esperance, then departs for Rabaul arriving August 16, 1942.

On August 22, 1942 departs Rabaul to patrol south of Samarai and then proceeds to Port Moresby. On August 26, 1942 LtCdr Kuriyama sends a regular situation report after arriving in his prescribed area. It is the last signal received from the RO-33. On September 1, 1942 the submarine is officially presumed lost off Port Moresby with the entire crew of seventy. In fact, RO-33 was depth charged and sunk on August 29, 1942 off Port Moresby.

Sinking History
On August 29, 1942 at 11:34 MV Malaita escorted by destroyer HMAS Arunta departed Port Moresby to escape enemy air raids and was steaming southward bound for Cairns. At 12:10pm near the entrance to Fairfax Harbor, MV Malaita was hit on her starboard side below the bridge by a torpedo fired by RO-33 at roughly at 9° 50' S, 144° 55' E and took on a heavy list to starboard. By 12:45pm, the crew abandoned the ship fearing she is about to capsize, but later re-boarded and the vessel was towed back to Port Moresby.

Searching for the attacking submarine, HMAS Arunta makes sonar contact with RO-33 ten miles southeast of Port Moresby and made four depth charge attacks releasing Mark VII depth charges. Afterwards, a large oil slick was observed at roughly 9°  36' S, 147° 6' E.

Wrecks & Reefs (1994) pages 199–207
Combined Fleet - IJN Submarine RO-33: Tabular Record of Movement

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Last Updated
August 8, 2021


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