After Italy declared war on Austria-Hungary and the other Central Powers in 1915, the three Radetzky-class ships bombarded coastal targets in the Adriatic Sea.

By the end of July 1905, the Austrian Commander in Chief of the Navy, Admiral Monteccuccoli, laid out his vision for an expanded Austro-Hungarian fleet.

While naval spending was growing rapidly after 1905, particularly a result of the patronage of Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne; he and Montecuccoli had succeeded in attracting public support,[2][3] neither the budgets of 1905 or 1906 included spending allocations for an additional class of battleships.

[5] In a speech to the Austrian Reichsrat in July 1906, Montecuccoli lobbied hard to put these slipways to use by saying, "The best defense of a coast lies certainly in a powerful offensive.

"[6] In November, Montecuccoli presented both the Austrian Reichsrat and the Diet of Hungary a new naval budget for the construction of three battleships with a displacement of 14,500 tonnes (14,271 long tons).

[11] However, Austro-Hungarian dock facilities at the time limited displacement to 16,000 long tons (16,260 t); the two "dreadnought" type designs were too heavy.

[10] Popper eventually relented, after admitting that the larger dreadnought type design would also warrant the construction of a new floating dry dock, which would significantly increase the cost of the project.

[11] Between August and November 1906, the Austro-Hungarian navy conducted explosive tests using the 30-year-old ironclad Kaiser Max.

The ships carried 1,350 long tons (1,370 t) of coal, which enabled a maximum range of 4,000 nmi (7,400 km; 4,600 mi) at a cruising speed of 10 kn (19 km/h; 12 mph).

A 54 mm (2.1 in) thick torpedo bulkhead ran the length of the hull to provide a second layer of underwater protection should the main belt be penetrated.

In 1912, Zrínyi took part in a training cruise with the recently commissioned dreadnoughts Tegetthoff and Viribus Unitis in the eastern Mediterranean, which included a stop at Malta.

By this time, the Austro-Hungarians had not yet fully mobilized their fleet, though the three Radetzkys and three Tegetthoffs, along with several cruisers and smaller craft, were available.

On 7 August, when the Germans broke out of Messina, the Austro-Hungarian fleet, including the Radetzky-class battleships, sailed as far south as Brindisi, before returning to port.

On 21 October, the ship arrived, and the gunfire from her 30.5 cm guns forced the French to abandon the position.

[16] On 24 May 1915, all three ships bombarded the Italian coast, including the important naval base at Ancona, following the entrance of Italy into the war on the side of the Triple Entente.

[17] By October 1918, Austria prepared to transfer her entire fleet to the State of Slovenes, Croats and Serbs in order to keep it out of Italian hands.

On 10 November 1918, one day before the armistice, Yugoslav officers with scratch crews sailed Radetzky and Zrínyi out of Pola.

The two battleships hoisted American flags and sailed south along the Adriatic coast to Castelli Bay near Spalato.

They appealed for American naval forces to meet them and accept their surrender, which a squadron of USN submarine chasers in the area did.