"All equipment of the [[British Army|[British] expeditionary force]] was lost, and we knew that there were few reserves of men and materiel in the homeland. Never in modern times had Britain been in a more critical situation. Only a man like Winston Churchill could have brought the country through such a crisis. We had no plans for an invasion and no equipment and specially trained forces with which to undertake the invasion. Hence the delay, the hesitation, and finally Hitler’s decision not to risk it. Whether we should have risked it is of course now only a matter of historical interest. Admiral Wagner, with whom I have discussed this question recently and who was then chief of Naval Operations, is of the opinion that it would have failed. I think it could have been done. Militarily, this was for us one of the lost opportunities of the war. With regard to the air attack in August and September [1940]—the Battle of Britain—I can speak only from the standpoint of the army. It was not thought possible to conquer Britain from the air. The objective was to destroy British air power and gain control of the air. This failed. English aircraft were greater in number than estimated or Britain’s production was higher than estimated. By the middle of September it was obvious that the attack against London would not be decisive. Our losses in aircraft from improved flank and other defense measures became too high in proportion to results achieved. The air attacks were then switched to new objectives—the production and armament plants became targets with a view of knocking out or delaying British rearmament. But in my opinion these were only substitute objectives fixed after the failure to achieve the first main objective—to destroy the British air power and gain control of the air over London and the south coast."
January 1, 1970
https://en.wikiquote.org/wiki/Adolf_Heusinger