Commissioned into service in the Italian Regia Marina (Royal Navy) in 1913, she served in World War I, playing an active role in the Adriatic campaign and seeing action in the Battle of the Strait of Otranto in 1917.

The squadron, under the command of Capitano de fregata (Frigate Captain) P. Orsini, was based at Taranto, although either Indomito or Impetuoso or both were visiting La Spezia that day.

[2] On 9 June 1915, Indomito, Impetuoso, Insidioso, Intrepido, Irrequieto, the protected cruiser Quarto, and the destroyers Animoso, Ardente, Ardito, and Audace escorted the armored cruisers Giuseppe Garibaldi and Vettor Pisani as they participated in the bombardment of the lighthouses at the Cape of Rodon and Shëngjin (known to the Italians as San Giovanni di Medua) on the coast of the Principality of Albania.

[4] On 3 December 1915 Indomito, Impetuoso , Insidioso, Intrepido, and Irrequieto got underway from Brindisi to escort one of the first supply convoys for Italian troops in Albania.

As the convoy — composed of the troop transports Re Umberto and Valparaiso, carrying a total of 1,800 men and 150 draft animals — approached Shëngjin (known to the Italians as San Giovanni di Medua) on the coast of Albania, Re Umberto, with 765 men on board, hit a mine laid by the Imperial German Navy submarine UC-14, broke in two, and sank in 15 minutes.

[4] On 9 June 1917 Indomito, now under the command of an officer named Da Sacco, escorted a convoy of merchant ships headed to Plataria, Parga, Murzo, and Igoumenitsa in the Epirus region of Greece carrying 1,700 men, 200 draft animals, and 300 tons of supplies.

[4] An Austro-Hungarian Navy force consisting of the scout cruiser Helgoland and the destroyers Balaton, Csepel, Lika, Orjen, Tátra, and Triglav left Cattaro on 18 October 1917 to attack Italian convoys.