Surrender of Caserta in the context of Mediterranean Theater of Operations, United States Army

The Italian Social Republic (Italian: Repubblica Sociale Italiana, IPA: [reˈpubblika soˈtʃaːle itaˈljaːna]; RSI, known prior to December 1943 as the National Republican State of Italy (Italian: Stato Nazionale Repubblicano d'Italia; SNRI), but more popularly known as the Republic of Salò (Italian: Repubblica di Salò, IPA: [reˈpubblika di saˈlɔ]), was a German puppet state with limited diplomatic recognition that was created during the latter part of World War II. It was a collaborationist regime in German-occupied Italy, established after the German invasion of Italy in September 1943 and disbanded with the surrender of Axis troops in Italy in May 1945. The German occupation triggered widespread national resistance against it and the Italian Social Republic during the liberation of Italy and the Italian civil war.

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

The Italian campaign of World War II, also called the Liberation of Italy following the German occupation in September 1943, consisted of Allied and Axis operations in and around Italy, from 1943 to 1945. The joint Allied Forces Headquarters (AFHQ) was operationally responsible for all Allied land forces in the Mediterranean theatre and it planned and led the invasion of Sicily in July 1943, followed in September by the invasion of the Italian mainland and the campaign in Italy until the surrender of the Axis forces in Italy in May 1945.

The invasion of Sicily in July 1943 led to the collapse of the Fascist Italian regime and the fall of Mussolini, who was deposed and arrested by order of King Victor Emmanuel III on 25 July. The new government signed an armistice with the Allies on 8 September 1943. However, German forces soon invaded northern and central Italy, committing several atrocities against Italian civilians and army units who opposed the German occupation and started the Italian resistance movement. Mussolini, who was rescued by German paratroopers, established a collaborationist puppet state, the Italian Social Republic (RSI), to administer the German-occupied territory. On 13 October 1943, the Allies recognized Italy as a co-belligerent in the war against Germany. Thereafter, the Italian Co-Belligerent Army and the Italian partisans fought alongside the Allies against German troops and the collaborationist National Republican Army; an aspect of this period is the Italian civil war. In the summer of 1944, after the Axis defeats at Cassino and Anzio, central Italy, including Rome, was liberated. Northern Italy was liberated following the final spring offensive and the general insurrection of Italian partisans on 25 April 1945. Mussolini was captured by the Italian resistance and summarily executed by firing squad. The campaign ended when Army Group C surrendered unconditionally to the Allies on 2 May 1945, one week before the formal German Instrument of Surrender. Both sides committed war crimes during the conflict, and the independent states of San Marino and Vatican City surrounded by Italian territory also suffered damage.

The Spring 1945 offensive in Italy, codenamed Operation Grapeshot, was the final Allied attack during the Italian Campaign in the final stages of the Second World War. The attack in the Lombard Plain by the 15th Allied Army Group started on 6 April 1945 and ended on 2 May with the surrender of all Axis forces in Italy.

The Mediterranean Theater of Operations, United States Army (MTOUSA), originally called the North African Theater of Operations, United States Army (NATOUSA), was a military formation of the United States Army that supervised all U.S. Army forces which fought in North Africa and Italy during World War II.

United States Army operations in the theater began with Operation Torch, when Allied forces landed on the beaches of northwest Africa on 8 November 1942, and concluded in the Italian Alps some 31 months later, with the German surrender in Italy on 2 May 1945. For administrative purposes, U.S. components were responsible to Headquarters North African Theater of Operations, United States Army (NATOUSA), which was created 14 February 1943. NATOUSA was redesignated Mediterranean Theater of Operations, United States Army (MTOUSA), on 26 October 1944.