Starting with the Invasion of Sicily in July of 1943, and culminating in the June 6, 1944, D-Day invasion of Normandy, Allied forces took the fight to the Axis powers in many locations across Western Europe. The push into Italy began in Sicily, but soon made it to the Italian mainland, with landings in the south.
The Italian government (having recently ousted Prime Minister Benito Mussolini) quickly signed an armistice with the Allies -- but German forces dug in and set up massive defensive lines across Italy, prepared to halt any armed push to the north. After several major offensives, the Allies broke through and captured Rome on June 4, 1944.