Following Mussolini's ouster in July and Italy's armistice with the Allies in September, the new Italian government under Marshal Pietro Badoglio declared war on Nazi Germany. The move plunged Italy into a brutal internal conflict, as German forces occupying the north fought both Allied troops and Italian partisans for the remainder of the war.
Italy's declaration of war on Germany on October 13, 1943, marked one of the most jarring reversals of World War II. Barely three years after joining Hitler as a founding Axis power, Italy found itself formally allied with Britain, the United States, and the Soviet Union against its former partner.
The road there had been chaotic. Mussolini was arrested in July 1943 after the Fascist Grand Council turned against him, and King Victor Emmanuel III installed Marshal Pietro Badoglio as prime minister. Badoglio secretly negotiated an armistice with the Allies, announced on September 8, prompting German forces to swiftly occupy Rome and much of the peninsula. Mussolini, rescued by German commandos, was installed as a puppet ruler in the north.
Italy's declaration of war on its former ally on October 13 gave the country's fledgling co-belligerent status legal form, and Italian troops, partisans, and resistance fighters would spend the next year and a half battling German occupiers alongside Allied forces as the front crawled slowly up the peninsula. The campaign proved brutal and slow, with fierce fighting at Monte Cassino and elsewhere, and Italy would not be fully liberated until the war's final weeks in 1945.
Key people: Pietro Badoglio, Victor Emmanuel III, Benito Mussolini