SM U-21 (U-XXI)

History

The First World War (1914-1918) was the last recorded operation of the Austro-Hungarian Navy, which had been in action since 1786. A committee was convened in 1904 to develop plans for indigenous submarines, but this and other plans were approved in a 1905 review. In the end, the service opted for an improved version of the existing German U-1, which became the Austro-Hungarian U-3.

From these modest beginnings, several other submarine types were developed before World War I, all based on foreign designs, such as the American C-class. As the conflict officially began with the assassination of Archduke Ferdinand in 1914, the Austrian navy was on high alert - although its U-boat force consisted of only six ships, two of which were not even operational.

Amid increasing wartime commitments, the Navy, under pressure to strengthen its underwater forces, pushed for a design based on the U-20 class, built in 1915-1917 and called for service in 1916-1918 . Four including "SM U-21" were completed. Although their status was usually obsolete by the time the war started, it was better to have a ship than nothing, and the local industry contracted to supply the submarines for the war service (the construction was split between the Austrian and Hungarian companies, which didn't help much).

U-21 displaces 170 long tons when surfaced and 210 long tons when launched. She is 127.1 feet long, has a beam of 13 feet, and has a draught of up to 9 feet. Power comes from a combined diesel-electric propulsion system, with a diesel generator set for surface operations and a battery-driven motor for underwater operations. The diesel system makes 450 horsepower, 160 of which comes from the electric motor.

These drive a shaft at the stern. The top speed is 12 knots on the surface and 9 knots underwater, with ranges of up to 1,400 nautical miles and 23 nautical miles, respectively. Internally, the ship has a crew of eighteen, consisting of officers and seamen.

Weapons are concentrated on 2 x 450mm torpedo tubes in forward bow mounts. In addition, the ship can use 66mm deck guns and 8mm machine guns for surface attack.

The U-21 was ordered on March 27, 1915, and the keel was laid shortly thereafterjust the stopgap needed by Austria-Hungary to deliver serviceable U-boats. She was launched on August 15, 1916, and officially commissioned on August 15, 1917. She was the first ship in the class to serve.

Like other Austro-Hungarian U-boats of World War I, the U-21's impact in the conflict proved to be rather small. From the beginning, she was plagued by self-inflicted injuries due to her design and her often inexperienced crew.

The damage forced her to be put on hold early in her career, and a leak ended one of her wartime patrols. During a voyage in July 1918, the ship encountered problems with the diesel engine and had to be towed to Bora for repairs. It remained that way until the armistice in November 1918.

After the surrender of Austria-Hungary, the U-21 was handed over to Italy as reparations, causing the submarine to devalue and eventually scrapped in 1920.

Specification

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AIR WING