HIS: This Day in History: 1943 – World War II: The Nazi puppet state known as the Italian Social Republic is founded.

The Italian Social Republic (Italian: Repubblica Sociale Italiana, RSI), popularly and historically known as the Republic of Salò (Italian: Repubblica di Salò [reˈpubːlika di saˈlɔ]), was a German puppet state with limited recognition that was created during the later part of World War II, existing from the beginning of German occupation of Italy in September 1943 until the surrender of German troops in Italy in May 1945.

The Italian Social Republic was the second and last incarnation of the Italian Fascist state and was led by Duce Benito Mussolini and his reformed anti-monarchist Republican Fascist Party. The state declared Rome its capital, but was de facto centered on Salò (hence its colloquial name), a small town on Lake Garda, near Brescia, where Mussolini and the Ministry of Foreign Affairs were headquartered. The Italian Social Republic exercised nominal sovereignty in Northern and Central Italy, but was largely dependent on German troops to maintain control.

In July 1943, after the Allies had pushed Italy out of North Africa and subsequently invaded Sicily, the Grand Fascist Council—with the support of King Victor Emmanuel III—overthrew and arrested Mussolini. The new government began secret peace negotiations with the Allied powers. When the Armistice of Cassibile was announced 8 September, Germany was prepared and quickly intervened. Germany seized control of the northern half of Italy, freed Mussolini and brought him to the German-occupied area to establish a satellite regime. The Italian Social Republic was proclaimed on 23 September 1943. Although the RSI claimed sovereignty over most of Italian territory, its de facto jurisdiction only extended to a vastly reduced portion of Italy. The RSI received diplomatic recognition from only Germany, Japan and their puppet states.

Around 25 April 1945, nineteen months after its founding, the RSI all but collapsed. In Italy, the day is known as Liberation Day (festa della liberazione). On that day, a general partisan uprising, alongside the efforts of Allied forces during their final offensive in Italy, managed to oust the Germans from Italy almost entirely. On 27 April, Italian partisans caught Mussolini, his mistress (Clara Petacci), several RSI ministers, and several other Italian Fascists, while they were attempting to flee. On 28 April, the partisans shot Mussolini and most of the other captives, including Petacci. The RSI Minister of Defense Rodolfo Graziani surrendered what was left of the Italian Social Republic on 1 May, one day after the German forces in Italy capitulated.