T4 was a seagoing torpedo boat operated by the Royal Yugoslav Navy between 1921 and 1932. Originally 79 T, a 250t-class torpedo boat of the Austro-Hungarian Navy built in 1914, 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, patrol, escort and minesweeping tasks, anti-submarine operations and shore bombardment missions. In 1917, the suffixes of all Austro-Hungarian torpedo boats were removed, and thereafter she was referred to as 79. Underway during the short-lived mutiny by Austro-Hungarian sailors in early February 1918, her captain realised the danger and put her crew ashore. She was part of the escort force for the Austro-Hungarian dreadnought during the action that resulted in the sinking of that ship by Italian torpedo boats in June 1918.
Following Austria-Hungary's defeat in 1918, 79 was allocated to the Navy of the Kingdom of Serbs, Croats and Slovenes, which later became the Royal Yugoslav Navy, and was renamed T4. 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, T4 and the rest of the navy were involved in training exercises and cruises to friendly ports, but activity was limited by reduced naval budgets. In 1932, she ran aground on the island of Drvenik Mali off the central Dalmatian coast and the hull broke in half. The bow remained on the island, and the stern was towed to the Tivat Arsenal in the Bay of Kotor. As a result, it became a standing joke among Yugoslav sailors that this made T4 the "world's longest torpedo boat". Eventually, both sections were scrapped where they were.
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 Triest was selected for the contract to build eight vessels, the T group, ahead of one other tenderer. The T-group designation signified that they were built at Triest.
Description and construction The , T-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 . Their designed displacement was , but they displaced about fully loaded. The boats were powered by two Parsons 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 and designed to propel the boats to a top speed of , although a maximum speed of could be achieved. They carried of coal and of fuel oil, which gave them a range of at . The T group had one funnel rather than the two funnels of the later groups of the class. The Austro-Hungarian Navy classified 79 T and the rest of the 250t class as high seas torpedo boats 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 originally to be armed with three Škoda L/30 guns, and three torpedo tubes, but this was changed to two guns and four torpedo tubes before the first boat was completed, to standardise the armament with the F group to follow. A searchlight was mounted above the bridge. The torpedo tubes were mounted in pairs, one between the forecastle and bridge, and the other on a section of raised superstructure above the aft machinery room. They could also carry 10–12 naval mines.
The sixth of its class to be completed, 79 T was laid down on 1 December 1913, launched on 30 April 1914, completed on 30 September 1914, and commissioned the following day, two months after World War I began. Before her commissioning, one Schwarzlose M.7/12 machine gun was included in the armament of all boats of the class for anti-aircraft work. Four mounting points were installed so that the machine gun could be fitted in the most effective position depending on the expected direction of attack. Until October 1915, the boat was painted black, but from that point it was painted a light blue-grey.
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 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. As the 250t-class boats came into service, they joined the 1st Torpedo Flotilla, which was initially led by the scout cruiser and later by her sister . The 1st Torpedo Flotilla initially included two divisions of destroyers (1st and 2nd) and a division of torpedo boats (3rd), which the 250t-class boats joined. Throughout the war, 79 T remained with the 3rd Torpedo Division of the 1st Torpedo Flotilla.
Not long after being commissioned, on 17 October 1914 79 T joined the rest of the 1st Torpedo Flotilla in an attempt to engage part of the French fleet operating in the southern Adriatic. The French were sailing in the vicinity of the island of Vis, but departed south during the night of 17/18 October, and the Austro-Hungarian flotilla was unable to launch an attack. Also in October, 79 T undertook a patrol between the islands of Busi and Pelagosa, and on 9 November the boat patrolled near the island of Lagosta. On 15 and 16 March 1915, 79 T, along with the old torpedo gunboat and 250t-class boats 75 T and 76 T, escorted the newly commissioned dreadnought battleship from the main Austro-Hungarian naval base at Polain the upper Adriaticto the island of Pago to conduct firing exercises. Led by Helgoland, the whole 1st Torpedo Flotilla steamed to the Ionian Sea over the period 11–15 April 1915 in search of the French fleet base, but the operation was unsuccessful.
Italy declared war on Austria-Hungary on 23 May 1915, and hostilities in the Adriatic, which had thus far mostly involved intermittent forays by the French fleet, immediately intensified. Almost the entire Austro-Hungarian fleet left Pola soon after the declaration to deliver an immediate response against Italian cities and towns along the Adriatic coast, aiming to interdict land and sea transport between southern Italy and the northern regions of that country which were expected to be a theatre of land operations. The fleet split into six groups with a range of targets up and down the coast. On 24 May, 79 T participated in this operation, known as the Bombardment of Ancona, which involved shelling of Italian shore-based targets; 79 T targeted Porto Corsini near Ravenna, along with the scout cruiser , Huszár-class destroyer , and 78 T, 80 T and 81 T. During that action, an Italian shore battery returned fire, hitting Novara and damaging 80 T, wounding three of her crew. Following this, 79 T was involved in several more attacks on Italian coastal targets, including one targeting Rimini on 18 June led by the armoured cruiser and the protected cruiser and supported by 75 T, 76 T and four s.
On 27 July, a group led by Novara and the scout cruiser , and escorted by the Huszár-class destroyers Scharfschutze and along with 79 T, 75 T and 76 T shelled the railway line between Ancona and Pesaro during a seaplane raid on Ancona. After the Italian airship Città di Jesi was downed on 5 August, 79 T towed her to Pola. On 17 August, the 1st Torpedo Flotilla shelled the island chain of Pelagosa in the middle of the Adriatic, and 79 T was part of a force tasked to protect the southern approaches to the islands from enemy submarines. The success of this bombardment, which destroyed the only source of drinking water, caused the Italians to abandon Pelagosa. On 9 September 1915, 79 T, 75 T and 76 T comprised the 3rd Torpedo Boat Group of the 3rd Torpedo Division. On 9 November, 79 T was sweeping for mines off Parenzo on the western coast of the Istrian peninsula when she was attacked unsuccessfully with a torpedo by an enemy submarine.
In late November 1915, the Austro-Hungarian fleet deployed a force from Pola to Cattaro in the southern Adriatic; this force included six of the eight T-group torpedo boats. This force was tasked to maintain a permanent patrol of the Albanian coastline and interdict any troop transports crossing from Italy. On 9 December, 79 T, three destroyers, two Kaiman-class torpedo boats and two other 250t-class boats formed a group led by Szigetvár which escorted seaplanes during a raid on Ancona. On 4 January 1916, 79 T laid mines in the Bay of Triest. A raid on the Otranto Barragean Allied naval blockade of the Strait of Otrantowas conducted by Novara, escorted by 79 T, 81 T, and the Kaiman-class boat 71 T on 3 April. On the night of 31 May/1 June 1916, the s and , accompanied by 79 T, 77 T and 81 T, raided the Otranto Barrage. Orjen sank one drifter with a torpedo, but once the alarm had been raised, the Austro-Hungarian force withdrew. After laying mines off the town of Rovigno in western Istria on 29 June, 79 T was transferred to the Bocche on 10 August.