Yes, successful invasion was possible in 1943. We had several successful amphibious invasions under our belts at this time. Any comparison with Gallipoli is just wrong. Anglo-American forces probably wouldn't have been able to reach the German border, or even the Meuse in '43, but we could have had a very large lodgement area complete with at least one major port. In fact, it would have probably been quite possible to take both Cherborg AND Antwerp (along with the Scheldt Estuary) As new divisions became ready they would have been shipped to France. Our side could have built up at least as fast, if not faster than Germany could and our divisions were better. I should also point out that then the British and Americans would have been able to fight the major battles on terrain that was much more advantagous to us than the coastal area of Normandy. Let's remember who the chief planner of Overlord was: Montgomery. His legacy is one of never taking a risk and fighting battles designed to make him look like a winner even if it cost more men in the process. What makes us think that they way things were done was the only way, or even the best way, of doing something?