Zara-class cruiser (1879)

Through the 1870s, the Marinekommandant (Navy Commander) of the Austro-Hungarian Navy, Friedrich von Pöck, could not secure sufficient funding for construction of ironclad warships. Unable to increase the strength of the ironclad fleet, Pöck turned to less expensive means to defend Austria-Hungary's coastline, including development of naval mines and self-propelled torpedoes. In March 1872, the Torpedoversuchs-Kommission (Torpedo Testing Commission) recommended to Pöck that a new warship should be built to use the Whitehead torpedo that had been developed in Austria-Hungary in the 1860s. Pöck decided to await a report from then-Fregattenkapitän (Frigate Captain) Hermann von Spaun, the naval attache to Britain, who was observing British developments, including the construction of the torpedo gunboat HMS Vesuvius. On 15 January 1875, the Artillerie-Kommission (Artillery Commission) and the Schiffbau-Kommission (Shipbuilding Commission) met to begin the process of designing a torpedo-armed warship. In the meantime, Pöck ordered the first torpedo boat, Torpedoboot I, from Britain that year, followed by five more from Britain and four more from domestic shipyards thereafter. The commissions were primarily concerned with several fundamental concerns, including whether the ship should be armored or not, whether it would only use the Whitehead torpedoes or it would also carry towed torpedoes, the propulsion system and whether it would include a sailing rig or not, and the speed the ship should be capable of reaching.[2][3]

The Schiffbau-Kommission recommended building a ship with heavy armor to protect it from enemy fire, one or two 10-centimeter (3.9 in) guns in the bow, deck-mounted launchers for the Whitehead torpedoes, and towed torpedoes to be used defensively against ramming. The launchers would be supplied with six torpedoes each. The ship would be capable of a speed of at least 15 knots (28 km/h; 17 mph) from a twin-screw propulsion system, and it would not be equipped with a sailing rig. They also created an alternate proposal for a smaller, unarmored ship with just two to four light guns, in the event that their preferred vessel could not reach the desired speed. The Artillerie-Kommission proposed a smaller design with sufficient armor and a high speed but no guns. They argued that an attempt to build what they described as a "universal battle-ship" (i.e., the Schiffbau-Kommission's first proposal) was ill-advised, since torpedoes were still in the developmental phase and a vessel of that type would be expensive and risky, considering the limited budgets of the time. The Torpedoversuchs-Kommission recommended a vessel with submerged torpedo tubes, a ram bow, deck and waterline belt armor, and two heavy gun turrets if it were possible to install them without compromising the ability of the ship to use its torpedoes effectively. Alternatively, if submerged tubes could not be made to work on the broad side, the ship should include two deck-mounted launchers with at least five torpedoes apiece, four heavy guns, and a speed sufficient just to keep pace with the ironclads of the main fleet.[4]

On 26 March, Pöck held a meeting to discuss the proposals. A suggestion was made to await developments in torpedo technology and to incorporate the weapons into the next ironclad that they could secure funding from Parliament to build. Josef von Romako, the Chief Constructor of the Austro-Hungarian Navy, pointed out that such a vessel would have to be very large to allow it to reach high enough speeds for it to be able to use torpedoes effectively. The meeting concluded with the consensus that the new vessel should be built as a purely torpedo-armed vessel, with no armor and no heavy guns. In the meantime, Spaun made his report on British naval activities, which included the completion of Vesuvius and the introduction of twin-screw propulsion. He also reported on the construction and sea trials of the British-built torpedo-aviso SMS Zieten for the Imperial German Navy. Zieten proved to be fast and maneuverable, qualities that made her well-suited to training and development of the German torpedo warfare arm. In January 1877, Pöck decided that the new vessel should incorporate the twin-screw, 15-knot requirement from the Schiffbau-Kommission proposal. On 30 January, Shipbuilding Engineer Andressen began working on the projet, which at that time included a pair of 24 cm (9.4 in) guns in an armored casemate. Pöck pointed out that the ship should not include heavy guns, and that two 12 cm (4.7 in) guns without armor would be sufficient; the only armor the ship was to have was a curved protective deck. Andressen prepared three more designs, as seen in the table below.[5]

Pöck rejected all of Andressen's proposals, since none of them incorporated the characteristics specified in the March 1875 meeting. Romako took over the design process in 1878, and prepared the design for Zara, construction of which began on 1 August that year. Romako based his design on the German Zieten, though the German vessel was significantly faster than the Zara class, in part owing to the fact that Zieten had a longer, finer hull and was more lightly built. In addition, the engines and boilers used in Zara and her sister ships could not tolerate as high a pressure as those in Zieten, and their boilers consumed coal excessively.[6]

Spalato in the 1880s or early 1890s

Owing to their poor performance and slow speed, the Zara-class cruisers did not see significant service with the fleet. They were too slow to be used as fleet scouts or flotilla leaders, and their gun armament was too weak for them to be able to protect torpedo boats from torpedo-boat destroyers. As a result, they spent most of the 1880s and 1890s laid up, being reactivated briefly for training exercises. Sebenico returned to active service in 1893, alternating between sea duty with the training squadron and harbor service as a training ship for engine-room personnel. In 1897, Spalato became assigned to the artillery school, while Zara was recommissioned for use in the torpedo school.[17] That year, Sebenico took part in the only significant period of fleet service, when she was sent to the island of Crete to participate in an international naval demonstration during Greco-Turkish War.[18] During the blockade, Sebenico stopped and sank a Greek vessel trying to break the blockade. Sebenico served in a variety of auxiliary roles over the following five years, before joining Spalato in the artillery school in 1903; the three ships served in their training roles until the outbreak of World War I in July 1914, at which point they became guard ships.[17]

The ships saw no action during the war, owing in large part to the nature of the Adriatic campaign. The Austro-Hungarian Navy and its primary opponent, the Italian Navy, both adopted cautious strategies, since neither wanted to risk its fleet in the narrow waters of the Adriatic Sea, where naval mines and fast, torpedo-armed craft could operate effectively.[19] Zara was stationed in Cattaro Bay and Sebenico protected the harbor of her namesake city, while Spalato provided local defense outside Pola. Zara was transferred from Cattaro Bay to Pola in June 1917, but while en route, suffered a serious explosion that caused significant damage to her bow. A contemporary investigation determined that it was the result of badly deteriorated chemicals in her torpedo warheads, though the naval historian René Greger reports that a mine was actually to blame. After repairs were effected, she joined the harbor defense at Pola. Sebenico was withdrawn from guard duties in 1918 and assigned to the torpedo school. All three ships were seized as war prizes by the victorious Allied powers after the war in 1918, and all three were awarded to Italy in 1920. Having no use for the vessels, the Italians immediately sold all three to ship breakers.[11][17]

• Bilzer, Franz F. (1990). Die Torpedoschiffe und Zerstörer der k.u.k. Kriegsmarine 1867–1918. Graz: H. Weishaupt. ISBN 978-3-900310-66-0.
• Gardiner, Robert & Gray, Randal, eds. (1985). Conway's All the World's Fighting Ships: 1906–1921. Annapolis: Naval Institute Press. ISBN 978-0-85177-245-5.
• Greger, René (1976). Austro-Hungarian Warships of World War I. London: Ian Allan. ISBN 978-0-7110-0623-2.
• Halpern, Paul G. (1995). A Naval History of World War I. Annapolis: Naval Institute Press. ISBN 1-55750-352-4.
• Sondhaus, Lawrence (1994). The Naval Policy of Austria-Hungary, 1867–1918. West Lafayette: Purdue University Press. ISBN 978-1-55753-034-9.