IJN I-21

IJN I-21 History

As an island nation, Japan's immediate success on the road to World War II (1939-1945) was largely due to the projection of its naval power. The massive naval build-up ensured that Japanese forces were able to seize what they wanted in the Asia-Pacific region before arranging a surprise attack on Pearl Harbor in Hawaii and attempting to isolate the Australian mainland.

The Japanese invasion of the mainland in early 1942 proved to be a very real threat to ordinary Australians.

Part of Japan's naval forces in the Pacific waters are B1-class submarines, including the "I-21". The ship was launched on January 7, 1939 under the management of the Kobe Kawasaki Shipyard in Japan, and on February 24, 1940.

Completed on 15 July 1941, the ship entered active duty and would become the most successful Japanese submarine on Australian soil, sinking some 44,000 tonnes of Allied cargo during its long career.

When constructed, the I-21 displaces 2,625 tons when surfaced and 3,715 tons underwater. She has a barrel length of 356.5 feet, a beam of 30.5 feet, and a draft of 16.9 feet. Propulsion is via a diesel-electric arrangement with 2 diesel engines for surface travel with an output of 12,400 hp and an electric motor for underwater travel with an output of 2,000 hp. Like other submarines of the era, the I-21 had to surface to release dangerous carbon dioxide gas, get fresh oxygen, and recharge its batteries.

After surfacing, the I-21 was able to travel at nearly 24 knots and reached 8 knots underwater. The range is 14,000 nautical miles, or about 26,000 kilometers, which gives her a good range. Therefore, strong ocean-going capability is a necessary condition for the design.

The hull is designed for depths up to 330 feet. Her crew consisted of 94 officers and was drafted into the army.

As an attack submarine, the I-21 was approved to use 6 x 533 mm (21 in) torpedo tubes in the bow-facing launchers, with three placed on one side of the hull. Seventeen torpedo reloads were made.

Surface warfare is handled by a 1 x 140mm deck gun, which proves useful against surface threats and offshore targets.

Unlike other submarines of the war, the I-21 also led reconnaissance missions, capable of launching a Yokosuka E14Y series seaplane for reconnaissance. This provided the I-21 with an "over-the-horizon" detection facility that could spot potential new targets for the ship to attack, or provide the Japanese naval command with the current movements and positions of allied forces.

I-21 was soon assigned to U-Boot-Division 3 (U-Boot-Geschwader 1) of the Sixth Fleet. She then became part of the Japanese fleet responsible for the December 7, 1941 raid on Pearl Harbor, Hawaii, to limit the capabilities of the U.S. Navy in the regionespecially its carrier group. As the operation progressed, I-21 provided much-needed patrols in northern Oahu on the day of the attack. After her partial success (the U.S. carrier fleet was not in port as planned), I-21 was aboard an unknown aircraft carrier and its supporting forces, but mechanical failure and aggressive Allied air cover kept her from engaging her prey . The I-21 was then reassigned to the U.S.

West Coast trade route, where it could harass incoming and outgoing merchants at will.

On December 23, 1941, I-21 gained an advantage over a passing tanker named SS Montebello and surprisingly sank her, while Montebello's crew was uninjured and managed to get on a lifeboat escape. On June 8, 1942, I-21 was ordered to attack the Newcastle Shipyard in New South Wales with deck guns.

While little damage was done, it showed that the vulnerability of key positions off Australia's coast was now within the reach of Japanese aggression. On January 17, 1943, I-21 sank SS Kalingo, killing two people - although about 32 managed to escape. On its January patrol route, I-21 managed to engage several other ships with good results, some damaged while others surrendered completely.

On February 8, 1943, I-21 attacked and sank the SS Iron Knights at sea, killing 36 crew members. Starr King was then sunk by I-21 near Port Macquarie on February 11, 1943.

I-21 continued wartime patrols for most of 1943 until around November, when the ship is believed to have been located by US Navy fighter jets (from USS Chenango) at Tarawa on 29 November 1943 , attack and sink. Although officially unconfirmed, it is believed to be the ship's I-21, and her crew has never heard from her again.

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