Their allegiance was to King Victor Emmanuel and Marshal of Italy (Maresciallo d'Italia) Pietro Badoglio, the men who ousted Mussolini.
The Italian Navy played an important role once the armistice was signed.
Nine cruisers, 33 destroyers, 39 submarines, 12 motor torpedo boats, 20 escorts, three mine-layers, and the seaplane tender Giusseppe Miraglia joined the Italian Co-Belligerent Navy.
There were additionally four squadrons of seaplanes from the Italian Royal Air Force (Regia Aeronautica).
Present within the Co-Belligerent Navy were the groups "Mariassalto", carrying on the legacy of the Decima Flottiglia MAS frogmen group on the allied side, and the "San Marco" brigade, who were the first allied forces to enter the city of Venice.