The first plan for an offensive campaign [in the West] was formulated in November 1939. In substance it was a repetition of the 1914 Schlieffen plan.… - Adolf Heusinger

The original timetable called for the launching of the campaign in May , with the objectives to be reached in five months—that is, in October. But the campaign did not begin until late June, bringing the terminal date into November. Originally, Hitler, the C in C, and the chief of the general staff agreed that wherever they stood in November, they would close down operations. However, they gambled with the weather, which in the late autumn was favorable, just as it was to Napoleon in 1812, and kept saying, ‘We can risk it’. Then came the bitter weather, and the German armies started to retreat.

As far as winter preparations were concerned, measures had been taken by the supply services, but they were inadequate. Clothing was prepared for a hard German winter, but it was inadequate for a severe Russian winter. The transport failed because German locomotives were not equipped for extremely low temperatures. Moreover the Russians in their retreat destroyed all the water tanks and this created enormous difficulties in train operations. The campaign should have been halted earlier and necessary measures taken to hold the positions already taken.

All equipment of the [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 —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.