On Quora Peter Stucki writes these fascinating remarks:

Stephen Bungay’s myth-busting work on the Battle of Britain, A Most Dangerous Enemy, mentions, at the end, a German general being interrogated by the Russians. They ask him what he thought the turning point was in the war. They expected him to say “Stalingrad”. Instead, he answered “The Battle of Britain”.

“…For example: Terraine states that the outcome was “decisive”; quoting Luftwaffe General Werner Kreipe, who described it as a “strategic (Luftwaffe) failure” and “turning point in the Second World War”. It also states the “German Air Force was bled almost to death, and suffered losses that could never be made good throughout the course of the war”. Quoting Dr (Karl) Klee “The invasion and subjugation of Britain was made to depend on that battle, and its outcome therefore materially influenced the further course and fate of the war as a whole”.[4]

…”

The Prussian military thinker, Von Clausewitz once said that “friction in war” can be decisive over time. He speaks of how a supposedly short trip by coach can suddenly become over long by rain on the roads slowing and exhausting the horses, leading to a late arrival at an inn, only to find fresh horses already taken, further delaying the trip. In similar manner, the Battle of Britain robbed many trained pilots from the upcoming invasion of Russia adding to that “friction”.

In war, VUCA (Volatility, Uncertainty, Complexity, Ambiguity) can lead to snowballing emergent effects, where, by the time Stalingrad arrives, an already weakened Luftwaffe becomes non-linearly more weakened had it not been for the Battle of Britain: Reconnaissance flights don’t spot Operation Uranus, supplying the trapped 6th Army by air is infeasible, Russians are getting much needed supplies via the US convoys protected by air and sea from air bases and harbors in Britain. Later on, at Kursk, a huge air battle, as large as the Battle of Britain, is fought, and the Germans fail to gain air superiority, a key element of Blitzkrieg.

Omar Bradley said “Amateurs talk strategy and tactics. Professionals talk about logistics”: The Battle of Britain created the opportunity for Allied logistics to begin take hold by allowing US industrial might to come to bear thanks to the “unsinkable aircraft carrier Britain” , while amplifying German industrial weakness. In a sense, the Battle of Britain started a hemorrhage that non-linearly weakened not only the Luftwaffe but all of Hitler’s efforts while strengthening those of the Allies.

Addendum: A comment mentions the Luftwaffe’s shift to bombing London as having saved the RAF from collapse. Stephen Bungay and other researchers have looked at Systems Dynamics simulations to model not only aircraft and pilot losses, but also aircraft production and training of both RAF and Luftwaffe over time.

What emerges is surprising: Though earlier researchers documented that aerodromes and radar infrastructure never stayed knocked out for long enough for the Luftwaffe to gain permanent air superiority, the thought was that the RAF would have eventually buckled. However, the simulations showed that the RAF + the world’s first Integrated Air Defense + logistics was indefinitely sustainable. Ironically it was the Luftwaffe whose losses in pilots and aircraft would, over time, lead to its collapse.

Systems Engineering of the Battle of Britain C2