Stalingrad is almost universally considered the turning point of the war. Germany took heavy losses in the actual battle, and millions more would follow in in the attempt to halt the march of the Russians. On the western front, D-Day was probably the most important. It gave the allies a huge advantage as now they could advance on Germany from two fronts. Also important was the Battle of Britain. The RAF successfully kept Great Britain in the war while putting huge losses on the Luftwaffe.