|Royal Marines at Pegasus Bridge, image found at:|
This question could be really simple to answer without going into great detail. Firstly Operation Overlord was the stepping stone the Allies needed to defeat Germany. They had to invade mainland Europe somewhere other than Italy, which turned out to be a tough old gut rather than the soft underbelly of Europe.
Caen was an objective which was supposed to have been taken on D-Day itself, but maybe it was an over ambitious objective? The British advanced from Sword Beach to 5km from Caen, they had landed 29,000 men and taken many prisoners. By noon the Juno, Sword and Gold beaches were consolidated into one large bridgehead. The British 6th Airborne had held onto Pegasus Bridge and the bridge at the River Orne and were relieved by Lord Lovat's Royal Marines. U.S paratroopers had caused havoc behind enemy lines even if most were dropped in the wrong areas. At Omaha beach, the Americans had encountered fierce opposition (352nd Infantry Division) and large numbers of beach obstacles and were nearly evacuated back onto the ships. At Utah Beach the American troops realised they had been landed in the wrong place, but took advantage of lighter opposition and made good progress inland.
Carentan, St Lo and Bayeux were objectives which were not captured on D-day, but the Allies were able to consolidate their foothold in France and land more men, vehicles and supplies on the beaches and by using the Mulberry Harbours. What did D-Day achieve? It helped end the war in Europe in less than 12 months from the 6th June 1944. We should not forget the sacrifice these people made.