D-day was an incredible Allied achievement that hastened victory over Nazi Germany. American officers were unanimous in their belief that only a huge army, landed as close as possible to the German border, to drive on Berlin, and hang Hitler from a sour apple tree, would bring victory. Americans, backed by a large and loyal population, endless fertile farmlands, plentiful natural resources, and the world’s largest industrial base, felt that this was possible, If German resistance was stiffer than anticipated, it could be crushed by sending more troops and tanks and guns, of which America had a goodly supply.
The Brits, who put up many of the troops for D-day and much of the airpower and shipping and naval support, had been fighting Hitler for five long years. They had learned, first hand and to their sorrow, how effective the German army was. Norway, Dunkirk, Tobruk, and The Blitz were not happy memories for the Brits. They counseled caution and thought the Americans were reckless in their outlook.
By 1944 the Allies had accomplished two major successes, both of which wee absolutely vital to the success of D-day. First they had solved the U-boat problem. In the “happy days” of 1941 and 1942, the U-boats were sinking hundreds of merchantmen every year. But in the winter of 1943 the Allies got their act together and drove the U-boats out of the Atlantic. They had allocated just a few B24 bombers, with extra fuel tanks in their bomb bays, to close the Atlantic air gap, the black pit the merchant seamen called it. The B24’s could supply good air cover to convoys all the way across the Atlantic. And all the destroyers had been equipped with good radar, Talk-Between-Ships (TBS) radio, and High Frequency Direction Finders (Huff-Duff) which gave a vector pointing right at any U-boat that used its radio. And two years experience at sea had trained up the escort vessels to a high pitch of effectiveness. A couple of vicious convoy battles in the winter of 1943 resulted in the Allies sinking more U-boats than the U-boats sank merchant vessels. For the rest of the war U-boat sinkings remained heavy. This victory allowed the Americans to build up a huge army on the British Isles. Had the U-boats sunk half of this traffic on the way across, D-day would have been impossible.
The second victory was the extermination of the Luftwaffe. This was done by the P-51 long range escort fighters that accompanied the bombers all the way to the target and shot down the Luftwaffe fighters that rose to attack the bombers. There is a scene in “The Longest Day” where a Luftwaffe fighter pilot complains that his was the only sortie flown against the Normandy beaches. Had the Luftwaffe been strong, the JU-88’s would have been dropping 500 pound bombs into the open landing craft as they approached the beaches, and on the Allied destroyers. For larger naval targets the Luftwaffe had Fritz-X, an early model smart bomb that had put an American cruiser out of action at Salerno and sunk an Italian battleship in the Mediterranean. But due to the RAF and USAF actions the Luftwaffe no longer had the planes, or the pilots, or the gasoline to oppose the D-day landings.
