6 June 1944 and the Allied invasion of Europe - D-Day, the return to Europe for the final and decisive battles against Nazi Germany. The scale of the amphibious operation was almost immeasurable, the risks were high, and success was by no means guaranteed. After years of build-up, planning and exercises, the Allies were about to storm a heavily-defended coast that had been occupied by the enemy for four years. It was an all-arms operation by land, sea and air forces, with, as usual, the land forces taking the greatest risks and highest casualties The air campaign in the build-up phase, from bombing to reconnaissance was crucial in preparing the battlefield; the air support of the actual assault, whilst not perfect, ensured there was no air threat; whilst the continued air effort in the weeks after D-Day helped ensure that once the Allies were ashore they would not be pushed back into the sea.