Yugoslav torpedo boat T2

At the outbreak of World War I on 28 July 1914, 77 T was part of the 1st Torpedo Group of the 3rd Torpedo Craft Division of the Austro-Hungarian 1st Torpedo Craft Flotilla,[9] which was led by the scout cruiser Saida commanded by Linienschiffskapitän (Captain) Heinrich Seitz, and supported by the mother ship Gäa.[10] 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.[11] 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.[12]

During the war, 77 T was used for convoy, patrol, escort and minesweeping tasks, anti-submarine operations,[1] and shore bombardment missions.[13] 77 T was transferred to Sebenico on 16 August.[14] In early September, intelligence was received by the Austro-Hungarian command that an Italian volunteer corps were planning to land on the Dalmatian or Istrian coast, and the 1st Torpedo Flotilla was involved in fruitless patrolling off Sebenico and Zara between 19 and 24 September. According to the naval historian Zvonimir Freivogel, this was disinformation that allegedly originated with the French and was intended to keep the Austro-Hungarian fleet engaged while the French conducted operations in the southern Adriatic undisturbed.[15] On the evening of 3 November, the 1st Torpedo Flotilla left Sebenico to make a night torpedo attack on the French fleet, which had begun its seventh raid on the Adriatic on 31 October. By the time they reached the threatened areas, the French had withdrawn as they were running low on coal.[16] On 6 November, 77 T conducted a patrol off the Dalmatian island of Lastovo, and returned to the main fleet base at Pola in the upper Adriatic on 23 December.[14]

On 10 May 1915, during the lead-up to the Italian declaration of war on Austria-Hungary, 77 T swept the approaches to the Italian port of Ancona for mines.[14] On the afternoon of 23 May, and almost the entire Austro-Hungarian fleet left Pola soon after 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.[17] On 24 May 1915, 77 T and seven other 250t-class boats participated in the Bombardment of Ancona, which involved shelling Italian shore-based targets, 77 T being involved in the operation against Ancona itself.[18] 77 T laid defensive mines off the Dalmatian port of Split on 6 June.[19] On the night of 18/19 June, separate Austro-Hungarian naval task groups attacked both Venice and Rimini, with distant cover provided by a group led by Saida and the scout cruiser Helgoland and consisting of three destroyers and five 250t-class boats, one of which was 77 T. Near San Benedetto del Tronto, this group intercepted and sank the Italian steamer Grazia.[20] Immediately after this operation, 77 T underwent a refit at Pola.[19] On 23 July, 77 T and another 250t-class boat participated in another shore bombardment mission led by Helgoland against Ortona on the central Adriatic coast of Italy.[21][lower-alpha 2] 77 T was involved in an attack on the island chain of Pelagosa in the middle of the Adriatic on 28 July.[19] On 17 August, the 1st Torpedo Flotilla again shelled Pelagosa, and 77 T was part of a force led by Saida 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.[23] 77 T again bombarded Pelagosa on 9 September. During September she conducted patrols between the islands of Lastovo, Pelagosa, and Biševo and the Italian port of Bari.[19]

In late November 1915, the Austro-Hungarian fleet deployed a force from Pola to Cattaro in the southern Adriatic; this group included six of the eight T-group torpedo boats. This force was tasked with maintaining a permanent patrol of the Albanian coastline and interdict any troop transports crossing from Italy.[24] After an attack on Durazzo in Albania in which two Austro-Hungarian destroyers were sunk after straying out of a cleared lane through a minefield, on 30 December 77 T and four other 250t-class boats were sent south with the scout cruiser Novara to strengthen morale and try to prevent the transfer of the captured crew of one of the destroyers to Italy. No Italian ships were encountered, and the group returned to the Bocche the following day.[25]

On 17 January 1916, 77 T salvaged a damaged Austro-Hungarian seaplane near the Montenegrin coastal town of Petrovac and towed it to the Bocche.[19] On 22 February, 77 T and two other 250t-class boats, accompanied by a Kaiman-class torpedo boat, laid a minefield outside the Montenegrin port of Antivari. With Austro-Hungarian forces closing on Durazzo from the land, the Allies began to evacuate by sea, and Austro-Hungarian naval forces were sent to attempt to interdict. On 24 February, Helgoland, four destroyers, 77 T and five other 250t-class boats were sent to intercept four Italian destroyers covering the evacuation, but were unable to locate them.[26] Between 11 March and 2 May 77 T underwent a further refit at Pola, and on 4 May was transferred to the Bocche.[19] On the night of 31 May – 1 June, the Tátra-class destroyers Orjen and Balaton, accompanied by 77 T and two other 250t-class boats, raided the Otranto Barrage, an Allied naval blockade of the Strait of Otranto. Orjen sank the British drifter Beneficent, but once the alarm had been raised, the Austro-Hungarian force withdrew.[27][28] 77 T laid mines off Cape Rodoni – north of Durazzo – on 29 June, and returned to Pola in July. On the night of 23/24 September, 77 T and three other 250t boats laid mines off the Po River estuary near Venice. On 12 October, 77 T was attacked by enemy aircraft about 19 km (12 mi) west of Pineda near Venice.[19]

In 1917, one of 77 T's 66 mm guns was placed on an anti-aircraft mount.[2] On 3 February 1917 she was transferred to the Bocche, and four days later she conveyed the German Vizeadmiral Hugo Kraft to Pola for an inspection. During a storm on 8 February, a crew member fell overboard in the Bay of Kvarner and drowned.[19] On 21 May, the suffix of all Austro-Hungarian torpedo boats was removed, and thereafter they were referred to only by their numeral.[1] 77 was again transferred to the Bocche on 17 August.[19] On 23 September 1917, 77 and another 250t-class boat were laying a minefield off Grado in the northern Adriatic when they had a brief encounter with a Royal Italian Navy (Italian: Regia Marina) MAS motor torpedo boat.[29] During 1917, 77 conducted two minesweeping operations and escorted thirty-six convoys.[19]

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. 77 was present in the anchorage,[30] and one of her crew raised a red flag, but the executive officer ordered the flag be lowered. The commanding officer of the group of four 250t boats including 77 to light their boilers, intending to order the boats to leave the vicinity of Sankt George and Gäa – which were both controlled by mutineers – but the mutineers ordered the boiler fires put out. The following day, while her commanding officer was absent, a red flag was again raised on 77. Other torpedo boats followed the lead of 77, but by 3 February the revolt was over, and the mutinous sailors were removed from all affected vessels. Five days later, 77 was transferred to Pola for repairs, but by 14–15 February was operational again, chasing a enemy submarine.[31]

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.[32] During the night of 8/9 June 1918, Horthy left Pola with the dreadnought battleships Viribus Unitis and Prinz Eugen. At about 23:00 on 9 June, after some difficulties getting the harbour defence barrage opened, the dreadnoughts Szent István and Tegetthoff,[33] escorted by one destroyer and six torpedo boats, including 77, 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,[lower-alpha 3] while returning from an uneventful patrol off the Dalmatian coast, two Italian MAS boats, MAS 15 and MAS 21, spotted the smoke from the Austro-Hungarian ships.[35] With their engines off, the two Italian boats waited for the lead ships of the starboard escort, the Huszár-class destroyer Velebit and 77, to pass, before launching their attack.[36] Both boats successfully penetrated the escort screen and split to engage the dreadnoughts individually. MAS 21 attacked Tegetthoff, but her torpedoes missed.[35] 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 of her boiler rooms, which flooded, knocking out power to the pumps. Szent István capsized less than three hours after being torpedoed.[34] 77 helped rescue survivors from Szent István.[31] This disaster essentially ended Austro-Hungarian fleet operations in the Adriatic for the remaining months of the war.[37] Soon after this event, Linienschiffsleutnant Armin Pavić took command of 77 – Pavić went on to reach the rank of kontraadmiral in the interwar Royal Yugoslav Navy (Serbo-Croatian Latin: Kraljevska mornarica, KM; Краљевска морнарица). During 1918, 77 conducted seven anti-submarine missions, six minesweeping operations, and escorted twenty-three convoys.[31]

The Austro-Hungarian Empire sued for peace in November 1918, and 77 survived the war intact.[1] Immediately after the Austro-Hungarian capitulation, French troops occupied Cattaro, which was treated by the Allies as Austro-Hungarian territory.[38] During the French occupation, the captured Austro-Hungarian Navy ships moored at Cattaro were neglected, and 77's original torpedo tubes were destroyed or damaged by French troops.[39] In 1920, under the terms of the previous year's Treaty of Saint-Germain-en-Laye, which officially ended the participation of rump Austria in World War I, she was allocated to the Kingdom of Serbs, Croats and Slovenes (later Yugoslavia).[40] Along with three other 250t-class T-group boats, 76, 78 and 79, and four 250t-class F-group boats, she served with the KM. Taken over in March 1921 when French forces withdrew,[39][40] in KM service, 77 was renamed T2.[2] When the navy was formed, she and the other seven 250t-class boats were the only modern sea-going vessels in the KM.[41] New torpedo tubes of the same size were ordered from the Strojne Tovarne factory in Ljubljana.[5]

In KM service it was intended to replace one or both guns on each boat of the 250t class with a longer Škoda 66 mm L/45 gun, and according to Freivogel this included the forward gun on T2. She was also fitted with one or two Zbrojovka 15 mm (0.59 in) machine guns. In KM service, the crew increased to 52,[5] and she was commissioned in 1923.[42] In 1925, exercises were conducted off the Dalmatian coast, involving the majority of the KM.[43] T2 underwent a refit in 1927.[42] In May and June 1929, six of the eight 250t-class torpedo boats accompanied the light cruiser Dalmacija, the submarine tender Hvar and the submarines Hrabri and Nebojša, on a cruise to the British Crown Colony of Malta, the Greek island of Corfu in the Ionian Sea, and Bizerte in the French protectorate of Tunisia. The ships and crews made a very good impression on the British while visiting Malta.[44] In 1932, the British naval attaché reported that Yugoslav ships engaged in few exercises, manoeuvres or gunnery training due to reduced budgets.[45] By 1939, the maximum speed achieved by the 250t class in Yugoslav service had declined to 24 kn (44 km/h; 28 mph),[5] and in that year T2 was stricken from the naval register due to her age and scrapped soon after.[46][42]