What was the turning point battle for the Allies in Europe?

Stalingrad is often seen as the key turning point. It was here that the Germans were halted. Due to Hitler's refusal to allow a strategic withdrawal the entire 6th army was captured. Only 6,000 ever returned.

However there are other possible answers. The tank battle at Kursk in the summer of 43, the largest battle of its type in history, ended in a stalemate, but in reality was a defeat for the Germans who needed to secure a victory.

One could also argue that the Battle of Britain was a turning point. The failure of the Luftwaffe to secure victory meant that Britain could continue the war as a German invasion was no longer possible.

D-Day in June 1944 is also crucial because it opened up a second front in Europe. However what is also often ignored are the landings in Southern Italy and indeed Southern France, all of which stretched the German forces.