[1] After promotion to lieutenant, Leonardi participated in World War I, first serving on board the armoured cruiser Francesco Ferruccio, then on the battleship Duilio and later in the Albania Naval High Command.

[1] When World War II broke out, Leonardi was the deputy commander of the La Spezia Arsenal.

[2] While British forces steamrolled towards Syracuse and the interior, Leonardi tried to organize a counter-attack in co-operation with German units, but on the night between 10 and 11 July – while Leonardi was absent from Augusta, having gone in the backcountry to organize the counter-attack – many the troops that manned the Augusta defences, and especially the units of the Coastal Artillery Militia (MILMART, a Blackshirt branch tasked with coastal defense, whose personnel was recruited locally, and whose morale was particularly low because of the dire conditions of their families and their fear of being executed for being Fascist) abandoned their posts, blew up batteries and fortifications, disbanded and went home.

[2] Leonardi himself was captured by British forces six days later and sent to a POW camp in Great Britain, where he remained till November 1944.

[1] The Salò Republic, however, looking for scapegoats in the military to justify the defeat of Italy, branded Leonardi as a traitor and a coward, falsely accusing him of having ordered the destruction of the coastal batteries and having surrendered Augusta without a fight; he was tried and sentenced to death in absentia by a Fascist kangaroo court in May 1944.