On July 10, 1943, the Allies begin their invasion of Axis-controlled Europe with landings on the island of Sicily, off mainland Italy. Encountering little resistance from the demoralized Sicilian troops, the British 8th Army under Field Marshal Bernard Law Montgomery came ashore on the southeast of the island, while the U.S. 7th Army under General George S. Patton landed on Sicily's south coast. Within three days, 150,000 Allied troops were ashore.
Italian leader Benito Mussolini envisioned building Fascist Italy into a new Roman Empire, but a string of military defeats in World War II effectively made his regime a puppet of its stronger Axis partner, Germany. By the spring of 1943, opposition groups in Italy were uniting to overthrow Mussolini and make peace with the Allies, but a strong German military presence in Italy threatened to resist any such action.
Meanwhile, Nazi leader Adolf Hitler knew that an Allied invasion of Nazi-controlled Europe was imminent, but because Germany's vast conquests stretched from Greece to France, Hitler was unable to concentrate his forces in any one place. In an elaborate plot to divert German forces away from Italy, a British submarine off Spain released the corpse of an Englishman wearing the uniform of a British major and carrying what appeared to be official Allied letters describing plans for an invasion of Greece. The body washed ashore, and the letters were sent by the Spanish to the German high command, who reinforced their units in Greece. The Axis had only 10 Italian divisions and two German panzer units on Sicily when Allied forces attacked in the early-morning hours of July 10.
First to land were American and British paratroopers and glider-borne troops, and at dawn thousands of amphibious troops came ashore. Coastal defenses manned by disaffected Sicilian troops collapsed after limited resistance, and the Anglo-Americans moved quickly to capture Sicily's southern cities. Within three days, the Allies had cleared the southeastern part of the island. In a pincer movement aimed at Messina in the northwest, the British 8th Army began moving up the southeast coast of the island, with the U.S. 7th Army moving east across the north coast. The Allies hoped to trap the Axis forces in the northwestern corner of Sicily before they could retreat to the Italian mainland. In the so-called "Race to Messina," Montgomery's advance up the southeast coast was slowed by German reinforcements, but Patton and the U.S. 7th Army moved quickly along the north coast, capturing Palermo, the Sicilian capital, on July 22.
In Rome, the Allied invasion of Sicily, a region of the kingdom of Italy since 1860, led to the collapse of Mussolini's government. Early in the morning of July 25, he was forced to resign by the Fascist Grand Council and was arrested later that day. On July 26, Marshal Pietro Badoglio assumed control of the Italian government. The new government promptly entered into secret negotiations with the Allies, despite the presence of numerous German troops in Italy.
Back in Sicily, Montgomery and Patton advanced steadily toward Messina, prompting the Germans to begin a withdrawal of Axis forces to the mainland. Some 100,000 German and Italian troops were evacuated before Patton won the race to Messina on August 17. Montgomery arrived a few hours later. The Allies suffered 23,000 casualties in their conquest of Sicily. German forces sustained 30,000 casualties, and the Italians 135,000. In addition, some 100,000 Axis troops were captured.
On September 3, Montgomery's 8th Army began an invasion of the Italian mainland at Calabria, and the Italian government agreed to surrender to the Allies. By the terms of the agreement, the Italians would be treated with leniency if they aided the Allies in expelling the Germans from Italy. Later that month, Mussolini was rescued from a prison in the Abruzzo Mountains by German commandos and was installed as leader of a Nazi puppet state in northern Italy.
In October, the Badoglio government declared war on Germany, but the Allied advance up Italy proved a slow and costly affair. Rome fell in June 1944, at which point a stalemate ensued as British and American forces threw most of their resources into the Normandy invasion. In April 1945, a new major offensive began, and on April 28 Mussolini was captured by Italian partisans and summarily executed. German forces in Italy surrendered on May 1, and six days later all of Germany surrendered.