What was the turning point in western front of war in Europe?

Some people might tell you that it was the Normandy Invasions, more commonly known as "D-Day". However, this question is open to interpretation.

Personally, I believe the Battle of Britain was the major turning point in the Western European Theatre. France had been defeated in three weeks, and the Russians were taking a beating as well. It wasn't looking good for the allies in the early stages of the war.

However, in order for the Germans to take Britain (and therefore control Western Europe entirely), they had to control the skies of the English Channel and knock out nearby British air bases; without this, British fighters and bombers could blow German transports during an amphibious assault right out of the water. As we all now know, however, the British were able to repel the Luftwaffe in one of the longest and greatest aerial battles of all time (the British owe a lot of their success to the recent development of the radar; this invention had come just in time for them, as they were able to tell where the Germans were coming from long before they crossed the English Channel). If Germany had successfully invaded England, it would turn the war into a full one-front war against the Russians, and Stalin could not win that war.

Now that the British held out, this gave the Americans a staging ground for an amphibious assault on the beaches of Normandy. We all know how the rest of the story goes.

Again, this is an interpretation. Some people might have other opinions.