Beginning with the invasion of Sicily in July of 1943, and with the D-Day invasion of Normandy on June 6, 1944, Allied forces fought against Axis powers in several locations in Western Europe.
The first Allied forces landed on the Italian peninsula on September 3, 1943, and Italy surrendered on September 8 (although the Italian Social Republic of Mussolini was soon established). On September 9, 1943, the 1st US Army landed in Salerno. The Germans launched a fierce counterattack.
US The 5th Army and other Allied forces broke through two German defensive lines (the Volturno and Barbara lines) in October and November 1943. After a heavy winter and the challenges faced by the Allies, Rome fell on June 4, 1944.
In May 1944, the Western Allies were ready to deliver their biggest blow of the war, the long-delayed, cross-Channel invasion of northern France, code-named Overlord. General Dwight D. Eisenhower was the supreme commander of the operation, which ultimately involved a coordinated effort of 12 nations.