[2] After Italy requisitioned the first four Vifor-class ships — the only four of the planned 12 ever constructed — the Italians completed them as scout cruisers to modified designs.

The power plant consisted of a pair of Tosi steam turbines and five Thornycroft boilers, generating a designed output of 40,000 shaft horsepower (29,828 kW) powering two shafts, which gave each ship a designed top speed of 34 knots (63 km/h; 39 mph), although the ships actually achieved between 35 and 38 knots (65 and 70 km/h; 40 and 44 mph), depending on the vessel.

[8] During World War I, she operated in the Adriatic Sea, participating in the Adriatic campaign against Austria-Hungary and the German Empire, taking part primarily in small naval actions involving clashes between torpedo boats and support operations for Allied motor torpedo boat and air attacks on Central Powers forces.

Dartmouth, the British light cruiser HMS Bristol, and the Italian destroyers Antonio Mosto and Giovanni Acerbi placed themselves between Aquila and the Austro-Hungarian ships and opened fire on them at 09:30 at a range of 8,500 metres (9,300 yd).

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

Aquila got underway from Brindisi with Antonio Mosto, Indomito, the scout cruiser Sparviero, the destroyer Giuseppe Missori, the British light cruisers HMS Gloucester and HMS Newcastle, and the French Navy destroyers Bisson, Commandant Bory, and Commandant Rivière to join other Italian ships in pursuit of the Austro-Hungarians, but after a long chase which also saw some Italian air attacks on the Austro-Hungarian ships, the Austro-Hungarians escaped and all the Italian ships returned to port without damage.

On 10 February 1918 Aquila, Ardito, Ardente, Francesco Stocco, Giovanni Acerbi, and Giuseppe Sirtori — and, according to some sources, the motor torpedo boat MAS 18 — steamed to Porto Levante, now a part of Porto Viro, in case they were needed to support an incursion into the harbor at Bakar (known to the Italians as Buccari) by MAS motor torpedo boats.

Sources disagree on the purpose of the operation: According to one, the three scout cruisers were tasked to operate about 15 nautical miles (28 km; 17 mi) west of Menders Point while the torpedo boats attacked Austro-Hungarian merchant ships about 15 nautical miles (28 km; 17 mi) to the east at Durrës (known to the Italians as Durazzo) on the coast of Albania,[8] while another claims that they were covering the recovery of a broken-down flying boat that had landed in the Gulf of Drin.

In the war's immediate aftermath, Aquila and Sparviero got underway from Brindisi and took possession of Hvar (known to the Italians as Lesina), an island off the coast of Dalmatia, on 15 November 1918.

[14][15] Shortly after 08:40, the destroyer Giuseppe Missori accidentally rammed F 14, causing F 14 to sink in the Adriatic Sea 7 nautical miles (13 km; 8.1 mi) west of the Brijuni archipelago.

[14][15] Aquila was among the first ships to arrive on the scene, and by dragging her anchor chain she helped speed up the identification of the location of the sunken — but largely unflooded —submarine, inside which 23 of the 27 crew members were trapped alive.

[14][15] When F 14′s hatches finally were opened, rescuers discovered that her entire crew had died, asphyxiated by carbon dioxide and chlorine gas.

[16] The Italians handed the two ships over to the Spanish crews in Sardinia on 11 October 1937,[16][17] although Aquila officially remained on the rolls of the Regia Marina, which reclassified her as a destroyer on 5 September 1938.

[5][7] To conceal the transfer, Italy did not make it official until January 1939, and the Spanish Nationalists took steps to confuse observers as to her identity: Her modifications at Castellammare di Stabia included the installation of a dummy fourth funnel to give her a greater resemblance to the four-funneled Velasco, and the Nationalists initially referred to her by the name "Velasco-M" rather than as Melilla.

[19][20] The flotilla was assigned to convoy escort duties, support to ground operations, the interdiction of merchant ships of the Spanish Republican faction, and antisubmarine patrols.

Through the end of 1937, Melilla sortied on numerous occasions to escort ships or convoys or patrol the coast, but mechanical breakdowns often forced her to return to port for repairs.

[16] Capitán de fragata (Frigate Captain) Francisco Regalado Rodríguez, a future admiral and Minister of the Navy, took command of the flotilla on 5 December 1937.

[16] On 7 January 1938, Melilla got underway from Palma de Mallorca with Ceuta and the heavy cruiser Canarias to rendezvous with the Republican merchant ship SAC-5, whose officers wanted to surrender to the Nationalists, but did not find SAC-5.

[16] On the afternoon of 22 February 1938 Melilla, Teruel, and Velasco escorted the merchant ship Pasajes, which was making a voyage in the Balearic Islands from Formentera to Mallorca.

[20] Escorting the cruiser division, Melilla got underway from Palma de Mallorca on the morning of 28 February 1938, to cover Velasco and the minelayers Jupiter and Vulcano as they laid a minefield off Valencia.

[16] In March 1938 Melilla was among the ships that escorted the auxiliary cruiser Rey Jaime II and the oil tankers Campuzano and Gobeo from Cádiz to Palma de Mallorca.

[16] Melilla′s transfer to the Spanish Nationalists became official and overt on 6 January 1939 when the Regia Marina struck her from the Italian navy list.

The Spanish Navy viewed them as lacking the mechanical reliability and fighting value to serve in combat and assigned them to training duties with the Naval Military Academy.