Emboldened by the Austro-Hungarian victory during the Battle of the Strait of Otranto, and determined to break the Otranto Barrage with a major attack on the strait, Austria-Hungary's newly appointed Commander-in-Chief of the Fleet Miklós Horthy organised a massive attack on the Allied forces with Admiral Spaun, alongside seven battleships, three cruisers, four destroyers, four torpedo boats, and numerous submarines and aircraft, but the operation was abandoned after the battleship Szent István was sunk by the Italian motor torpedo boat MAS-15 on the morning of 10 June.

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

Following the Armistice of Villa Giusti in November 1918, Admiral Spaun was seized by the Allies and transferred to Italy, where she participated in a victory parade through the Venice Lagoon in March 1919.

[5] During the first decade of the 20th century, Austria-Hungary's naval policy began to shift away from simply coastal defence, to projecting power into the Adriatic and even Mediterranean Seas.

New railroads had been constructed through Austria's Alpine passes between 1906 and 1908, linking Trieste and the Dalmatian coastline to the rest of the Empire and providing the interior of Austria-Hungary with quicker access to the sea than ever before.

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.

[7][8] Franz Ferdinand's interest in naval affairs stemmed primarily from his belief that a strong navy would be necessary to compete with Italy, which he viewed as Austria-Hungary's greatest regional threat.

[14] tonnage ratio Admiral Spaun first conceived on paper in early 1905 when Montecuccoli drafted his first proposal for a modern Austrian fleet as part of his plan to construct a navy large enough to contest the Adriatic Sea.

[18] Montecuccoli believed that should Austria-Hungary be drawn into a larger naval conflict encompassing the Mediterranean, Admiral Spaun would still be capable of fulfilling her role successfully and that a class of battlecruisers was not necessary for such a scenario.

These turbines were designed to provide 25,130–25,254 shp (18,739–18,832 kW)[a] and were powered by 16 Yarrow water-tube boilers, giving Admiral Spaun a top speed of 27.07 knots (50.13 km/h; 31.15 mph) during her sea trials.

Her smaller armament was due in part because of a desire within the Austro-Hungarian Navy for Admiral Spaun to have a faster speed and greater armour than most other contemporary cruisers of the era.

[18] In September 1909, Montecuccoli proposed to the Austro-Hungarian Ministerial Council a budget for 1910 which would authorise construction on the three cruisers of the Novara class, alongside the four dreadnoughts of the Tegetthoff-class battleships and several torpedo boats and submarines.

While Montecuccoli's desire to construct a new class of cruisers was delayed, this time due to the financial costs Austria-Hungary took on following the annexation of Bosnia and the mobilisation of her fleet and army at the height of Bosnian crisis, the navy was given funds to speed up completion of the Radetzky-class battleships and Admiral Spaun.

Austria-Hungary strongly opposed this as a Serbian port on the Adriatic could drastically alter the balance of power in the region, bring Serbia and Italy closer together through economic ties, and also serve as a Russian naval base.

By the end of November 1912, the threat of conflict between Austria-Hungary, Italy, Serbia, and Russia, coupled with allegations of Serbian mistreatment of the Austro-Hungarian consul in Prisrena led to a war scare in the Balkans.

[33] The crisis eventually subsided after the signing of the Treaty of London, which granted Serbia free access to the sea through an internationally supervised railroad, while at the same time establishing an independent Albania.

[34] In June 1914, the battleship Viribus Unitis was tasked with transporting Archduke Franz Ferdinand to the Condominium of Bosnia and Herzegovina in order to watch military manoeuvres.

[36] Upon hearing of the assassination, Marinekommandant Anton Haus sailed south from Pola with an escort fleet comprising Admiral Spaun, Viribus Unitis's sister ship Tegetthoff, and several torpedo boats.

Two days after their murders, Ferdinand and Sophia's bodies were transferred aboard Viribus Unitis, which had been anchored waiting to receive the Archduke for his return, and were transported back to Trieste.

While relations between Austria-Hungary and Italy had improved greatly in the two years following the 1912 renewal of the Triple Alliance,[41] increased Austro-Hungarian naval spending, political disputes over influence in Albania, and Italian concerns over the potential annexation of land in the Kingdom of Montenegro caused the relationship between the two allies to falter in the months leading up to the war.

[43] Shortly after the onset of the war, the assistance of the Austro-Hungarian fleet was called upon by the German Mediterranean Division, which consisted of the battlecruiser Goeben and light cruiser Breslau.

[51] This concern was so great to Haus that he wrote in September 1914, "So long as the possibility exists that Italy will declare war against us, I consider it my first duty to keep our fleet intact.

[56] However, engine and other machinery problems related to her propulsion systems hindered Admiral Spaun's abilities to be deployed for operations in the Adriatic in a similar fashion to the ships of the Novara class.

"[18] Instead, the ships of the Novara class continued operations in the Adriatic, conducting missions such as towing U-boats out into the Mediterranean or raiding Allied convoys and drifters guarding the Strait of Otranto.

On 20 May, Emperor Franz Joseph I gave the Austro-Hungarian Navy authorisation to attack Italian ships convoying troops in the Adriatic or sending supplies to Montenegro.

[75] En route to the harbour at Islana, north of Ragusa, to rendezvous with the battleships 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.

[84] Emperor Karl I, still attempting to save the Empire from collapse, agreed to the transfer, provided that the other "nations" which made up Austria-Hungary would be able to claim their fair share of the value of the fleet at a later time.

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 in Pola.

[87] Control over the battleship, and 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.