The channel islands could never be defended ,It is a fact that no enemy trod their jackboots on the UK mainland. I am sure that if the other vets here were asked "could we defned our Isle".The answer would be no....After dunkirk we had nothing. It is on record that the MOD gathered together all they could to make one Division a fully equipped unit (Third Div) THose days were full of imminent danger At Britain's weakest point, just after the fall of France on 22 June 1940, Germany had no sea-lift capability, no troops trained for amphibious operations, no specialised equipment - and no staff planning. UK had at least two ready divisions, and enough hardware (small arms, artillery) to field about 250,000 troops in unarmoured formations. The RN remained largely intact and had about 60 units in home waters ready to interdict a crossing attempt. Three months later in September - the start of the Battle of Britain - Germany still only had a rudimentary plan and a collection of completely inadequate sea-lift assets concentrated - the infamous Rhine barges, etc. UK had about five divisions fully armed by then, and about another 500,000 men under arms (depending how you classify units under training, etc). Again, the RN had about 80 units on standby. For a reality check, just look at the effort that had to go into D Day - even when the allies had 5,000+ dedicated ships, a million men available, and overwhelming air power... Whatever the mood in UK during 1940, or whatever is perceived as result of the whole WW2 "legend", the military facts are extremely clear: the Germans were never capable of achieving more than a suicidal airborne bridgehead, and UK's defences were relatively strong even at their weakest point. Note that not a single German general is known to have even bothered to take Sea Lion seriously.... Edited to add: with regard to the OP question, I think most Hitler biographers conclude that he wasn't even expecting the fall of France, but rather expected vaguely to be concluding an armistice with UK/France from the strength of occupied territory similar to WW1. Whilst he ordered the preparation of Sea Lion, it appears to have been simply on the basis of exploiting an unexpected situation. The fact that it took less than three months for him to completely abandon the idea - instead spending the entire time planning Barbarossa - arguably indicates that he'd never contemplated more than a continental land defeat of UK. There is no evidence at all of long-term pre-planning for a UK invasion, ie the concentration of war material, the build up of sea power, the full integration of his three fighting services, etc.