Enrico Toti was one of four Balilla-class submarines built for the Regia Marina (Royal Italian Navy) during the late 1920s.

[4] During the Spanish Civil War, the submarine unsuccessfully attacked the 1,011-gross register ton (GRT) cargo ship SS Bétis on 9 August 1937 during a patrol off Valencia.

HMS Triad was a T-class submarine of the Royal Navy that had set sail from Malta on 9 October 1940 under the command of Lieutenant-Commander G.S.

In the early hours of 15 October at 38°16′N 17°37′E / 38.267°N 17.617°E / 38.267; 17.617, off the Gulf of Taranto, she encountered the Enrico Toti, commanded by Lieutenant-Commander Bandino Bandini.

[6] Bandini, the officer on watch at the time, sighted the Triad on the surface at 01:00, and sounded battle stations on board the Italian submarine.

[6] In an account of the engagement published in 1940, Italian writer and then navy war correspondent Dino Buzzati, who interviewed the Enrico Toti officers and crew after their return to base, reports that both submarines were so close that an Italian gunner, furious because he could not yet train the gun to the British submarine, actually threw his shoes at the head of a British gunner.

[6] At this stage, Lieutenant-Commander Salt began to dive his ship, however she was sunk during this manoeuvre by two direct shell hits from the 120 mm gun.

From March to June 1942, Enrico Toti was transferred to the Italian naval base at Pola, where she carried out 93 training sorties.