He dedicated his political life to defending Venetian possessions in the Balkans from the Ottoman Empire.

When the second Ottoman siege of Corfu occurred in 1716, he was mainly responsible for strengthening Venetian fortifications that successfully resisted the attack.

During his second tenure, he managed to extend Venetian Dalmatia into the hinterland, taking the areas of Signo, Imoschi and Vrgorac.

He is memorialised on a 1728 Venetian monument affixed to the Defensive Wall of the New Fortress of Corfu Town, displaying above the Lion of Saint Mark (the symbol of Venice) and the arms of Diedo.

[3] It is inscribed in Latin as follows: ("To God, most good, most great, Alvise III Mocenigo, Duke of the Venetians (i.e. Doge); Marco Antonio Diedo (or Marcantonio Diedo), Supreme Governor (Venetian Provveditore Generale da Mar 1728-31 ("Superintendent General of the Sea"));[3] Giorgio Grimani, Commander of the Fleet; the first ordered this (i.e. the Wall); the second planned it; the third, by labour day and night, quickly completed it").