Was D-Day necessary?
The D-Day invasion started slowly but achieved major breakthroughs within two months of the landings. The German Army was massively engaged on both the east (Russia) and west (US & Britain) as well as in Italy, and it collapsed within a year. In the absence of the landings in France it would have lasted longer, although things were already going poorly against the Russians. A major concern of the US & Britain was not to allow the Russians (their ally at the time) to overrun all of Europe and set up communist governments, so it was important for them to get their armies into Europe in that sense.
