How did the allied campaign in italy prepare for the ground invasion of france on d-day?

D-Day Invasion started on June 6, 1944. The Allies prospered in redeeming France, Belgium, and Luxembourg. The troops battled their way onto a 60-mile stretch of beach in Normandy. The Germans had quarried in with machine guns, rocket launchers, and cannons and lived behind tangible walls which are three feet thick.