At the time of Italy's entry into the Second World War, in June 1940, he was in Rhodes, and shortly thereafter he was replaced by General Michele Scaroina at the command of the Regina Division and given command, on 10 September 1940 of the 101st Motorized Division "Trieste", stationed in the Po Valley.[17][18][19][20] In December 1940 he was promoted to major general and sent to Albania where he commanded an ad-hoc Special Alpine Division which helped halt the Greek offensive towards Vlore, for which he was awarded the Officer's Cross of the Military Order of Savoy.[21][22][23] In March he was repatriated and resumed command of the Trieste Division, which was then shipped to North Africa, where Piazzoni later commanded the groupment formed by the Trieste Division and the 132nd Armoured Division "Ariete", called Corpo d'Armata di Manovra, during the siege of Tobruk and the early stages of Operation Crusader.[24][25][26]
^In: The Central Registry of War Criminals and Security Suspects, Consolidated Wanted Lists, Part 2 – Non-Germans only (March 1947), Uckfield 2005 (Naval & University Press, facsimile edition of the original document at the National Archives in Kew/London), pp. 63, 65, 69.