Most people in history class have learned about the Nazi German bombing of London and other British cities during WWII, but was Germany planning an invasion of the British Isles? And do you think it would have worked?
Alison Brooks wrote a scathing examination of Operation Sea Lion, Why Sealion is Not an Option for Hitler to Win the War. The rules say that I should not just post a link without saying what's in it, but it's hard to give it thorough coverage, because it's a thorough dismantling of the entire notion that Germany could have successfully invaded the UK, and it's worth reading if you're at all interested in the topic. Some features:
The Germans gathered low-freeboard river barges, swamping in anything more than Sea State 2 (and the Channel is notoriously stormy), with soldiers in the barges for some 30 hours (and not enough sailors to staff them). So the wake from one fast British destroyer could have sunk them.
The German Army and Navy were set up to have lousy command and interference with each other.
The English beaches had defences that were utterly outdated, the Royal Military Canal and the Martello Towers, which would be totally obsolete against German briding equipment or artillery, respectively ... except the Germans were not planning to bring bridging equipment or artillery, so they would have been quite effective.
The provisions for beach command were derisory: whatever lower officers were present would be expected to gather units and press for objectives, and high staff were explicitly expected to stay behind for a while.
The Luftwaffe was supposed to keep off the Royal Air Force, keep off the Royal Navy, keep off the UK's Army by acting as artillery ... simultaneously ... and if they failed in any one of them, the entire operation would be massacred. And they were supposed to also devastate London to make the population flee and choke the roads. "One presumes that, in their copious free time, the Luftwaffe pilots would eat three Shredded Wheat for breakfast."
"In this exercise, carried out in good visibility, with no enemy, in good weather, after travelling only a short distance, with no navigation hazards or beach defences, less than half the troops were got ashore where they could have done what they were supposed to do. The exercise was officially judged to have been a 'great success'."
Et cetera. It ends
We can choose to wave a magic wand, and wipe out the RN and the RAF, and examine how successful the invasion was likely to be in their absence. Sandhurst has done this on four occasions to my knowledge. Both sides were given the historical starting positions, with an invasion date of 24 September.
In each case, the details of the fighting varied, but by each analysis resulted in 27 September dawning with the Wehrmacht holding two isolated beachheads, one at roughly 2 divisions strength on Romney March, and one of 1 division at Pevensey. Each were opposed by more numerous forces, with growing numbers of tanks and artillery. German resupply was still across open beaches.
Operation Sealion can only be described as a blueprint for a German disaster.
In another article, she apparently coined the term Alien space bats: " 'Alien space bats' originally was used as a sarcastic attack on poorly written alternate histories due to lack of plausibility. ... Alison Brooks (1959-2002) is credited as the creator of the term, using it to debunk the possibility of a successful Operation Sea Lion by saying the only way it could be successful was if alien space bats helped the Nazis."
The invasion of Great Britain was planned out, but it wasn't feasible or realistic and most German generals put little stock in the belief it could ever actually be achieved. The simple truth is that even putting aside the British navy the Luftwaffe simply couldn't achieve the necessary air dominance over Great Britain to make it feasible. Now, putting aside the lack of control over the skies and ignoring the British navy we still come across the problem of running and supplying an army across a channel and eventually doing so in the face of increasingly treacherous terrain as we push further and further inland. Also until this point Russian has been entirely ignored, and while debatable, likely was preparing for some form of offensive action between 1941-42. Thus with the numerous caveats and ignorance required by the German High Command the only conclusion that can be drawn is that it was put on paper only so that the idea could be viewed and summarily dismissed.