As it has been mentioned before, in order for Germany to even consider an invasion of Great Britain, air superiority would have to be achieved.

Without this, nothing was possible as the mighty Royal Navy was simply too much for Germany.

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The war against Russia will be such that it cannot be conducted in a knightly fashion. This struggle is one of ideologies and racial differences and will have to be conducted with unprecedented, unmerciful and unrelenting harshness. -Adolf Hitler