When Austria-Hungary was facing defeat in the war in October 1918, the Austrian government decided to transfer the bulk of her navy to the newly formed State of Slovenes, Croats and Serbs in order to avoid having to hand the ship over to the Allies.

However, the appointment of Archduke Franz Ferdinand – heir to the Austro-Hungarian throne and a prominent and influential supporter of naval expansion – to the position of admiral in September 1902 greatly increased the importance of the navy in the eyes of both the general public and the Austrian and Hungarian Parliaments.

[4][5] Franz Ferdinand's interest in naval affairs were largely motivated from his belief that a strong navy would be necessary to compete with Italy, which he viewed as Austria-Hungary's greatest regional threat.

Furthermore, a major scandal involving the Terni steel works' armor contracts led to a government investigation that postponed several naval construction programs for three years.

[20] As a result, the largest shipbuilding enterprises in Austria-Hungary, the Witkowitz Ironworks and the Škoda Works, offered to begin construction on Tegetthoff and two other dreadnoughts at their own financial risk, in return for assurances that the Austro-Hungarian government would purchase the battleships as soon as funds were available.

After negotiations which involved the Austro-Hungarian joint ministries of foreign affairs, war and finance, the offer was agreed to by Montecuccoli, but the number of dreadnoughts constructed under this arrangement was reduced to just Tegetthoff and Viribus Unitis.

[21] In his memoirs, former Austrian Field Marshal and Chief of the General Staff Conrad von Hötzendorf wrote that due to his belief that a war with Italy in the near future was likely, construction on the battleships should begin as soon as possible.

He also worked to secure agreements to sell both Tegetthoff and Viribus Unitis to, in his words, a "reliable ally" (which only Germany could claim to be) should the budget crisis in Budapest fail to be settled quickly.

[22] Although smaller than the contemporary dreadnought and super-dreadnought battleships of the German Kaiserliche Marine and the British Royal Navy, Tegetthoff was part of the first class of its type in the Mediterranean and Adriatic Seas.

This was done in order to rush the completion of the Radetzky-class battleships, though the looming construction of three other dreadnoughts in addition to Tegetthoff meant the Austro-Hungarian Navy would likely have to ask the government for a yearly budget much higher than 100 million krone.

[27][28] Facing potential backlash over constitutional concerns that the construction of Tegetthoff committed Austria-Hungary to spend roughly 60 million Kronen without prior approval by either the Austrian Reichsrat or the Diet of Hungary, the deal remained secret.

[29] In the event of the agreement being leaked to the press prior to the passage of a new naval budget, Montecuccoli drafted several explanations to justify construction of the battleship and the necessity to keep its existence a secret.

The underwater protection system consisted of the extension of the double-bottom upwards to the lower edge of the waterline armor belt, with a thin 10-millimetre (0.4 in) plate acting as the outermost bulkhead.

[39] The British Admiralty considered the rumored construction of Tegetthoff and Viribus Unitis "as a concealed addition to the German fleet", and interpreted the ships as Austria-Hungary's way of repaying Germany for her diplomatic support during the former's annexation of Bosnia in 1908.

[41] These concerns continued to grow and in April 1909, British Ambassador Fairfax Leighton Cartwright asked Austro-Hungarian Foreign Minister Alois Lexa von Aehrenthal about the rumored battleships.

[42] Neither the Admiralty's suspicions, nor those of some politicians, managed to convince Parliament that the German government was attempting to use Tegetthoff and Viribus Unitis to escalate Germany and Britain's already contentious naval arms race however.

[33][49] Prior to World War I, Tegetthoff and her sister ship Viribus Unitis served as the pride of the Austro-Hungarian Navy, conducting several missions across the Adriatic and Mediterranean Seas as members of the First Battle Division under the command of Vice-Admiral Maximilian Njegovan.

[54][52] Upon hearing of the assassination of Archduke Franz Ferdinand and his wife Sophie on 28 June in Sarajevo, Commander-in-Chief of the Navy Anton Haus sailed south from Trieste with an escort fleet composed of Tegetthoff, the cruiser Admiral Spaun, and several torpedo boats.

While relations between Austria-Hungary and Italy had improved greatly in the two years following the 1912 renewal of the Triple Alliance,[57] increased Austro-Hungarian naval spending, political disputes over influence in Albania, and Italian concerns over the potential annexation of land in the Montenegro caused the relationship between the two allies to falter in the months leading up to the war.

Even so, the necessity of ensuring that Tegetthoff had the coal she needed in the event of an Italian or French attack or a major offensive operation resulted in her and other battleships remaining at port unless circumstances necessitated their deployment at sea.

[70][67] In early 1915 Germany suggested that Tegetthoff and the other battleships of the Austro-Hungarian Navy conduct an attack on the Otranto Barrage in order to relieve pressure on the Ottoman Empire at the height of the Gallipoli Campaign.

Furthermore, Italian ships stationed in Venice were effectively trapped by the positioning of the Austro-Hungarian fleet, preventing them from sailing south to join the bulk of the Entente forces at the Otranto Barrage.

Horthy's strategic thinking differed from his two predecessors, and shortly after assuming command of the navy he resolved to undertake a major fleet action in order to address low morale and boredom, and make it easier for Austro-Hungarian and German U-Boats to break out of the Adriatic into the Mediterranean.

Planning to repeat his successful raid on the blockade in May 1917,[91] Horthy envisioned a massive attack on the Allied forces with Tegetthoff and her three sister ships providing the largest component of the assault.

[93] En route to the harbour at Islana, north of Ragusa, to rendezvous with Viribus Unitis and Prinz Eugen for the coordinated attack on the Otranto Barrage, Szent István and Tegetthoff attempted to make maximum speed in order to catch up to the rest of the fleet.

Thus Emperor Karl I's government in Vienna asked the newly formed State of Slovenes, Croats and Serbs for help maintaining the fleet stationed at Pola and keeping order among the navy.

The transfer to the State of Slovenes, Croats and Serbs began on the morning of 31 October, with Horthy meeting representatives from the South Slav nationalities aboard his flagship, Viribus Unitis.

The head of the newly-established navy for the State of Slovenes, Croats and Serbs, fell to Captain Janko Vuković, who was raised to the rank of admiral and took over Horthy's old responsibilities as Commander-in-Chief of the Fleet.

[110] Following Nazi Germany's incorporation of Austria via the Anschluss of March 1938, Adolf Hitler used Austria-Hungary's naval history to appeal to the Austrian public and obtain their support.

[115] In reference to her originally planned name and in homage to the Austro-Hungarian Navy, the bell from Tegetthoff was presented to the German cruiser Prinz Eugen on 22 November 1942 by the Regia Marina.