The participation of Italy in the Second World War was characterized by a complex framework of ideology; politics; and diplomacy; in which its military history took place often heavily influenced by external factors. The imperial ambitions of the Fascist regime; which aspired to restore a 'Roman Empire' in the Mediterranean (their Mare Nostrum); collapsed due to defeats in Greece and East and North Africa. In 1943 Benito Mussolini was ousted and arrested by order of King Victor Emmanuel III; provoking a civil war.

The northern half of the country was occupied by Germans and made a collaborationist puppet state (with more than 600;000 soldiers); while the south was governed by monarchist and liberal forces; which fought for the Allied cause in the Italian Co-Belligerent Army (at its height numbering more than 50;000 men); helped by circa 350;000 partisans of disparate political ideologies that operated all over occupied Italy.