T7 was a sea-going torpedo boat operated by the Royal Yugoslav Navy between 1921 and 1941. Originally 96 F, a 250t-class torpedo boat of the Austro-Hungarian Navy built in 1915–1916, she was armed with two guns and four torpedo tubes, and could carry 10–12 naval mines. She saw active service during World War I, performing convoy escort, patrol, and minesweeping tasks, and anti-submarine operations. In 1917 the suffixes of all Austro-Hungarian torpedo boats were removed, and thereafter she was referred to as 96.
Following Austria-Hungary's defeat in 1918, 96 was allocated to the Navy of the Kingdom of Serbs, Croats and Slovenes, which later became the Royal Yugoslav Navy, and was renamed T7. At the time, she and the seven other 250t-class boats were the only modern sea-going vessels of the fledgling maritime force. During the interwar period, T7 and the rest of the navy were involved in training exercises and cruises to friendly ports, but activity was limited by reduced naval budgets. The boat was captured by the Italians during the German-led Axis invasion of Yugoslavia in April 1941. After her main armament was modernised, she served with the Royal Italian Navy under her Yugoslav designation, conducting coastal and second-line escort duties in the Adriatic Sea. Following the Italian capitulation in September 1943, she was handed over by the Germans to the Navy of the Independent State of Croatia. While sailing to Rijeka for a refit, she was attacked and driven aground by British Royal Navy small high-speed craft in June 1944 and then destroyed by the British Army to prevent her salvage. She was broken up in situ in 1953.
Background In 1910, the Austria-Hungary Naval Technical Committee initiated the design and development of a coastal torpedo boat, specifying that it should be capable of sustaining for 10 hours. At the same time, the committee issued design parameters for a high seas or fleet torpedo boat of , top speed of 30 kn and endurance of . This design would have been a larger and better-armed vessel than the existing Austro-Hungarian s. The specification for the high seas torpedo boat was based on an expectation that the Strait of Otranto, where the Adriatic Sea meets the Ionian Sea, would be blockaded by hostile forces during a future conflict. In such circumstances, there would be a need for a torpedo boat that could sail from the Austro-Hungarian Navy (, ) base at the Bocche di Cattaro (the Bocche or Bay of Kotor) to the strait during the night, locate and attack blockading ships and return to port before morning. Steam turbine power was selected for propulsion, as diesels with the necessary power were not available, and the Austro-Hungarian Navy did not have the practical experience to run turbo-electric boats. Despite having developed these ideas, the Austro-Hungarian Navy then asked shipyards to submit proposals for a boat with a maximum speed of . Stabilimento Tecnico Triestino (STT) of Trieste was selected for the contract to build the first eight vessels, designated as the T-group. Another tender was requested for four more boats, but when Ganz & Danubius reduced their price by ten per cent, a total of sixteen boats were ordered from them, designated the F-group. The F-group designation signified the location of Ganz & Danubius' main shipyard at Fiume.
Description and construction
The F-group boats had short raised forecastles and an open bridge, and were fast and agile, well designed for service in the Adriatic. They had a waterline length of , a beam of , and a normal draught of . While their designed displacement was , they displaced fully loaded. The boats were powered by two AEG-Curtis steam turbines driving two propellers, using steam generated by two Yarrow water-tube boilers, one of which burned fuel oil and the other coal. There were two boiler rooms, one behind the other. The turbines were rated at with a maximum output of and were designed to propel the boats to a top speed of . They carried of coal and of fuel oil, which gave them a range of at . The F-group had two funnels rather than the single funnel of the T-group. 79 T and the rest of the 250t class were classified as high seas torpedo boats by the Austro-Hungarian Navy, despite being smaller than the original concept for a coastal torpedo boat. The naval historian Zvonimir Freivogel states that this type of situation was common due to the parsimony of the Austro-Hungarian Navy. They were the first small Austro-Hungarian Navy boats to use turbines, and this contributed to ongoing problems with them, which had to be progressively solved once they were in service. The crew consisted of three officers and thirty-eight enlisted men. The vessel carried one yawl as a ship's boat.
The boats were armed with two Škoda L/30 guns, with the forward gun mounted on the forecastle, and the aft gun on the quarterdeck. A searchlight was mounted above the bridge. They were also armed with four torpedo tubes mounted in pairs, with one pair mounted between the forecastle and bridge, and the other aft of the mainmast. One Schwarzlose M.7/12 machine gun was carried for anti-aircraft work. Four mounting points were installed so that the machine gun could be mounted in the most effective position depending on the expected direction of attack. The boat could also carry 10–12 naval mines.
96 F was the second-to-last of the F-group to be completed, and was laid down at Ganz-Danubius' shipyard at Porto Re on 24 February 1915, launched on 8 July 1916 and commissioned at Ganz-Danubius' main shipyard at Fiume on 10 November of that year.
Career
World War I The original concept of operation for the 250t-class boats was that they would sail in a flotilla at the rear of a cruising battle formation, and were to intervene in fighting only if the battleships around which the formation was established were disabled, or in order to attack damaged enemy battleships. When a torpedo attack was ordered, it was to be led by a scout cruiser, supported by two destroyers to repel any enemy torpedo boats. A group of four to six torpedo boats would deliver the attack under the direction of the flotilla commander.
In 1917, one of 96 Fs 66 mm guns may have been placed on an anti-aircraft mount. According to the naval historian Zvonimir Freivogel, sources vary on whether these mounts were added to all boats of the class, and on whether these mounts were added to the forward or aft gun. On 12–13 March, 96 F conducted an anti-submarine patrol between the islands of Olib and Silba off the northern Dalmatian coast. She escorted the armoured cruiser from the Bay of Telašćica on the island of Isola Lunga to the main Austro-Hungarian Navy base at Pola in the northern Adriatic on 1 May. On 11 May, the British submarine stalked 96 Fs T-group sister ship 78 T off Pola, firing two torpedoes at her. The British captain had kept his submarine's periscope extended too far and for too long, and the tell-tale "feather" had alerted the crew of 78 T, allowing her crew to avoid the incoming torpedoes. 96 F, 78 T and 93 F, accompanied by the Huszár-class destroyer , unsuccessfully pursued the British submarine. That night, Csikós, 96 F, 78 T and 93 F were pursued and briefly engaged in the northern Adriatic by a force of Italian destroyers consisting of , , , and but the Austro-Hungarian force was able to retire to safety behind a minefield. On 21 May, the suffix of all Austro-Hungarian torpedo boats was removed, and thereafter they were referred to only by the numeral. From 19 to 24 May, 96 provided cover for the salvage of the Austro-Hungarian submarine SM U-5 after it had been sunk by a mine. On 3 June, the Huszár-class destroyers and Csikós, along with 96 and another 250t-class boat, had a brief encounter with three Italian MAS boats off the mouth of the Tagliamento river in the far north of the Adriatic.
On 3–4 June, 96, along with 93, and Csikós, Wildfang and their sister ship were returning from a seaplane support mission when Wildfang struck a mine and sank about southwest of the Pinida lighthouse on the eastern coast of Istria, with 96 assisting with the rescue of 25 of her 74 surviving crew. In June and July, Austro-Hungarian aircraft were constantly in action bombing various targets along the east coast of Italy. On a twenty-one seaplane raid targeting the harbour at Grado between Venice and Triest, and the main railway hub in the same area at Cervignano, 96 was part of the covering force which also included the Huszár-class destroyers , and , and the 250t-class boats 76, 80 and 92. Turul was targeted by an enemy submarine, but evaded the torpedo. From 18 August, 96 was based at Đenovići in the Bocche. On 29 November, 96, 83, 97 and Csikós were escorting the steamer Dalmatia when the convoy was attacked by a submarine just west of the mouth of the Bojana river, which forms the border between Montenegro and Albania. All four torpedoes missed.
On 1 February 1918, a mutiny broke out among the sailors of some vessels of the Austro-Hungarian Navy at the Đenovići anchorage within the Bocche, largely over poor food, lack of replacement uniforms and supplies, and insufficient leave, although the poor state of the Austro-Hungarian economy and its impact on their families was also a factor. 96 was based at Đenovići at the time, and initially her crew was indecisive about joining the revolt, which was suppressed the following day. On 17 March, 96 was supporting a seaplane reconnaissance mission, when the seaplane A87 was forced to land off Muzil near Venice, and 96 towed the aircraft to Pola. On 4 April, 96 towed a launch carrying a detachment of sailors from Pola to near Ancona, with the mission of landing and capturing one or more Italian MAS motor torpedo boats, but the sailors were landed too far north of Ancona, their beached launch was discovered by an Italian airship and towed to Ancona, and two of the sailors defected. The mission failed and the sailors were captured.
By 1918, the Allies had strengthened their ongoing blockade on the Strait of Otranto, as foreseen by the Austro-Hungarian Navy. As a result, it was becoming more difficult for the German and Austro-Hungarian U-boats to get through the strait and into the Mediterranean Sea. In response to these blockades, the new commander of the Austro-Hungarian Navy, Konteradmiral Miklós Horthy, decided to launch an attack on the Allied defenders with battleships, scout cruisers, and destroyers. During the night of 8 June, Horthy left Pola in the upper Adriatic with the dreadnought battleships and , with an escort that included 96. At about 23:00 on 9 June 1918, after some difficulties getting the harbour defence barrage opened, the dreadnoughts and , with an escort force, also departed Pola and set course for Slano, north of Ragusa, to rendezvous with Horthy in preparation for a coordinated attack on the Otranto Barrage. About 03:15 on 10 June, while returning from an uneventful patrol off the Dalmatian coast, two Royal Italian Navy () MAS boats, MAS 15 and MAS 21, spotted the smoke from the Austrian ships. Both boats successfully penetrated the escort screen and split to engage the dreadnoughts individually. MAS 21 attacked Tegetthoff, but her torpedoes missed. Under the command of Luigi Rizzo, MAS 15 fired two torpedoes at 03:25, both of which hit Szent István. Both boats evaded pursuit. The torpedo hits on Szent István were abreast her boiler rooms, which flooded, knocking out power to the pumps. Szent István capsized less than three hours after being torpedoed. This disaster essentially ended major Austro-Hungarian fleet operations in the Adriatic for the remaining months of the war. On 11 June, 96s sister 91 stranded on the Pelješac peninsula in southern Dalmatia, and 96 towed her to Pola.