Departing New London, Connecticut on 7 September 1943, Dace arrived at Pearl Harbor on 3 October, and 17 days later sailed on her first war patrol, bound for the southeast coast of Honshū and the approaches to Nagoya.

Dace put to sea on her third war patrol on 18 March, and two days later embarked a group of commandos at Langemak Bay.

For the next week, she scouted the coast around Hollandia (currently known as Jayapura), New Guinea, landing the commando parties and taking them back on board at night.

On 9 July, Dace scored at least three hits on a large transport whose two escorts dropped a total of 43 depth charges, badly shaking the submarine but causing little physical damage.

That night, she reestablished contact and just after midnight on 27 July, Dace launched an attack, firing ten torpedoes into a convoy of three merchantmen, sinking the tanker Kyoei Maru No.

She topped up her fuel tanks at Darwin, Australia on 10 September, and sailed for the exacting task of sweeping mines in Palawan Passage and Balabac Strait.

Continuing to track their target, hoping for a chance to finish off Takao, the two submarines worked through the Palawan Passage.

She scouted along the Singapore-Hong Kong shipping lane, then sailed on to mine the channel between Palau Gambir[7] and the mainland.

Three days later, while preparing to attack an eight-ship convoy, Dace was violently shaken by four depth charges or bombs.

Coming into attacking position, Dace saw the convoy also included three escorts, but continued to close the freighter, firing her first spread at only 380 yd (350 m).

She swung to fire at the tanker as the freighter, Hakuyo Maru (1,391 GRT), exploded and sank,[8][9][10] then was confronted by an escort apparently planning to ram.

After training men of the Marina Militare, she was decommissioned at New London on 31 January 1955, and transferred the same day to Italy under the Military Assistance Program.

Together with Enrico Tazzoli (ex-USS Barb), Leonardo da Vinci formed the backbone of Italian submarine strength in the late 1950s and 1960s.

[11] In addition to the Navy Unit Commendation, Dace received seven battle stars during her seven war patrols, the last five of which were designated as "successful."