The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

but it was certainly a proportion. Others were hit by stray bullets streaking
across the sky as aircraft tangled and turned in a dogfight.
Without doubt, however, most people were shot down without having
ever seen the enemy. ‘It was always the one you didn’t see,’ says Pete
Brothers, ‘that shot you down.’ This was how 609 Squadron lost so many
pilots in July; by turning the tables they then got their own back once the
August battles began.
This was why altitude was the most important tactical advantage of all
for the attacker. With height, a pilot could position himself in the best
possible position to attack – that is, with the sun behind him, making him
blind to the aircraft below. The Me 109, above all other aircraft, was ideal
for this. A pilot could swoop down, hammer an unsuspecting flight of
Spitfires or Hurricanes with a big punch, then quickly climb away again out
of danger and repeat the process.
In contrast with the men of Fighter Command, all the Luftwaffe fighters
had to do was shoot down Spitfires and Hurricanes, and they had the very
best aircraft with the right armament to do the job. They could – and should
– have been winning hands down, but by denying their natural advantages
Göring was effectively forcing them to fight with their hands tied behind
their backs. They were becoming the hunted rather than the hunters.
Their primary role was no longer to shoot down British fighters, but to
protect the bombers. Fighters, designed to be offensive weapons, were
being made to play a defensive role instead. In their panic – and because of
their lack of tactical understanding – the Luftwaffe High Command failed
to realize that by shooting down Spitfires and Hurricanes their fighters
would have been protecting the bombers. It was an unforgivable mistake.