- Bogart, Charles H.
- Ship histories and stories, WWII operations
- RAN Ships
- HMAS Yarroma, HMAS Sea Mist, HMAS Kuttabul
- March 1985 edition of the Naval Historical Review (all rights reserved)
This history of the Japanese submarine I27 was written by United States member of the Society, Charles H. Bogart. I27’s operations are of particular interest to Australia as she participated in the Battle of the Coral Sea, the midget submarine attack on Sydney Harbour and the sinking of merchant shipping on the east coast.
AT 0645 ON 7 DECEMBER 1941, the American destroyer Ward (DD139) fired the first shots of the Pacific War when she attacked and sank a Japanese midget submarine operating in restricted waters off the entrance to Pearl Harbor.
Lying in wait that day in the waters around Oahu were 28 fleet submarines of the Imperial Japanese Navy. This concentration represented almost half of Japan’s total submarine strength of 60, only 48 of these were capable of long range offensive action. The other 12 were obsolescent, suitable only for training or home defense operations.
Recognizing the need for additional submarines, Imperial Naval Headquarters had under construction in December 1941 29 submarines, of which 18 were slated for delivery in 1942 and the remainder in 1943. Funds had also been recently obtained by the Imperial Navy for the construction of an additional 38 submarines to be laid down in 1942.
Among the submarines under construction was I27, a type B1 boat. She traced her ancestry back to the KD2 type via the KD3s, KD4s and KD5s and represented the most successful fleet submarine built by Japan.
The KD2 type was a modification of World War German U-139 allocated to Japan at the end of the war.
As built I27 displaced 2,198 tons. Her hull was 356 ft. long with a beam of 30½ ft. and a draft of 16¾ ft. Diesel engines of 12,400SHP gave her a surface speed of 23½ knots while electric motors of 2,000SHP drove I27 at a speed of 8 knots submerged. Armament consisted of 5.5in/50, two single 25mm AA guns and six 21in bow torpedo tubes with 11 reloads. Located in front of her conning tower was a pressurized cylinder which could carry one seaplane or midget submarine.
Radius of action for I27 was 14,000 miles at 16 knots on the surface and 96 miles at 3 knots submerged. The crew consisted of 100 officers and men. A total of 20 boats of the type B1 class were built — 115, 117, 119, 121, 123, and 125–39.
The aircraft carried by I27 was a small one-man seaplane with a speed of 90 mph and an operational period of three hours. The aircraft could be launched 15 minutes after the submarine surfaced but recovery took an hour. The fragile construction of the aeroplane led to damage when it landed. Because of the long time needed to recover the aircraft upon its return it was often abandoned by the submarine at the completion of its combat mission.
I27 was ordered under the 1939 Naval Armament Replacement Plan which had been enacted in response to the US Navy’s new ship building programme. Ordered under this program were 26 submarines, 15 of them B1 type. Construction of I27 was awarded to the Sasebo Naval Yard. She was launched on June 6 1940 but was not commissioned until 24 February 1942. On that day under the command of Commander Iwao Yoshimura she and 128 were assigned to the newly activated Sub Div 14 of Sub Ron 8. By 1 March 1942, 129 and 130 had been added to Sub Div 14. Sub Ron 8 was assigned to the 6th Fleet and consisted of Sub Div 1, 3, and 14. Flagship of Sub Ron 8 was 110 while Hie Maru served as the tender.
March 1942 brought Sub Ron 8 its first operational orders. Its boats were assigned two tasks. The first task was to attack British warships based on the east coast of Africa and then engage in raids on merchant ships in the Indian Ocean.
The second was to attack Allied fleet units in the waters off Australia, New Zealand, New Caledonia and Fiji and to sink any merchant shipping in the area. To carry out this order Rear Admiral Ishizaki Noboron commanding Sub Ron 8 formed three task groups, KO detachment built around Sub Div 1 (116, 118, 120 and reinforced by 110 and 130) would carry out the Indian Ocean raid, while Hei Detachment formed from Sub Div 3 (121, 122, 124) and Otsu detachment consisting of Sub Div 14 with I27 would raid the South Pacific.