Ro-33 was an Imperial Japanese Navy Ro-33-class submarine. Completed and commissioned in November 1935, she served during World War II in the South China Sea, Indian Ocean, and southwestern Pacific Ocean and operated in support of Japanese forces in the invasion of British Malaya, the invasion of Java, the Battle of the Coral Sea, the Guadalcanal campaign, and the New Guinea campaign. She was sunk in August 1942 during her fifth war patrol.
Design and description
The submarines of the K5 sub-class were versions of the preceding KT sub-class with greater surface speed. They displaced surfaced and submerged. The submarines were long, had a beam of and a draft of . They had a diving depth of .
For surface running, the boats were powered by two diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, the K5s had a range of at ; submerged, they had a range of at .
The boats were armed with four internal bow torpedo tubes and carried a total of ten torpedoes. They were also armed with a single L/40 anti-aircraft gun and one Type 93 anti-aircraft machinegun.
Construction and commissioning
Ro-33 was laid down on 8 August 1933 by the Kure Naval Arsenal at Kure, Japan, as the lead submarine of the Ro-33 class. She was launched on 10 October 1934 and was named Ro-33 that day. She was completed and commissioned on 7 October 1935.
Service history
Pre-World War II
Upon commissioning, Ro-33 was attached to the Maizuru Naval District. On 31 May 1937 she was reassigned to Submarine Division 21 in the Sasebo Naval District. On 9 April 1938 she got underway from Sasebo, Japan, for a training cruise in southern Chinese waters that concluded with her arrival at Kīrun, Formosa, on 14 April 1938. Submarine Division 21 was reassigned to the Combined Fleet on 15 December 1938 and to Submarine Squadron 2 in the 2nd Fleet on 8 April 1939. Ro-33 was placed in the Second Reserve in the Sasebo Naval District on 15 November 1939.
Ro-33 returned to active service on 1 May 1940, with Submarine Division 21 reassigned to Submarine Squadron 5 in the 4th Fleet. She departed Sasebo on 16 May 1940 for a lengthy training cruise in the Caroline Islands, Marshall Islands, and Mariana Islands which concluded with her arrival at Yokosuka, Japan, on 22 September 1940. She participated in a naval review at Yokohama, Japan, on 11 October 1940. Submarine Division 21 was reassigned to Submarine Squadron 4 on 15 November 1940.
Ro-33 and her sister ship were placed in Third Reserve at Sasebo, Japan, on 15 May 1941, and while in reserve Ro-33 relieved Ro-34 as flagship of Submarine Division 21 on 21 May 1941. From mid-October through early November 1941 she underwent repairs and a refit at Maizuru Naval Arsenal in Maizuru, Japan. After the work was complete, she returned to active service, probably in mid-November 1941.
World War II
The Pacific Campaign of World War II began on 7 December 1941 (8 December 1941 in East Asia) with the Japanese attack on Pearl Harbor, Hawaii. At 16:00 on 8 December 1941, Submarine Division 21 — Ro-33 and Ro-34 — departed Sasebo bound for Cam Rahn Bay in Japanese-occupied French Indochina, which Ro-33 reached on 14 December 1941.
First war patrol
On 21 December 1941, Ro-33 got underway from Cam Ranh Bay to begin her first war patrol, assigned an operating area in the South China Sea east of Singapore in support of the Japanese invasion of British Malaya. Her patrol was uneventful, and she departed her patrol area on 5 January 1942 to return to Cam Ranh Bay, where she arrived on 7 January 1942.
Second war patrol
On 13 January 1942, Ro-33 departed Cam Ranh Bay for her second war patrol, bound for a patrol area in the South China Sea southeast of Anambas and west of Java. After another quiet patrol, she returned to Cam Ranh Bay on 30 January 1942.
Third war patrol
Ro-33 began her third war patrol on 8 February 1942, putting to sea from Cam Ranh Bay and again ordered to patrol off Anambas, in the same area as the submarine . Attached to the A Unit along with Ro-34 on 9 February 1942, she arrived in her patrol area on 10 February 1942.