The Germans could not pull this off, heres why.
1. During the invasions of Denmark and Norway, neither of which were a) at war, or b) with any significant military force, the Kriegsmarine lost a heavy cruiser, 2 light cruisers, 10 destroyers, 4 submarines, and 21(!) transport ships. Both battleships were put out of action as well. This leaves the Germans with only half the Royal Navy’s strength in the North Sea alone, throw in the British Mediterranean fleet, and that falls to a quarter. Even if the RN takes no part in the battle, the German navy literally didn’t have enough ships for cross channel supply of an invasion force big enough to destroy Britain, and the British would know an attack is coming, unlike the Norwegians. Germany even still was crippled at Narvik.
2. An amphibious invasion takes years, not months to prepare. This is evident when the two biggest naval powers, accompanied by total air supremacy over the channel combined with cutting edge landing technology and a willing participant in the resistance groups planned Overlord for two years and still incurred massive losses. The Germans were using glorified rowboats and had no to seriously plan for an attack before France fell. The Germans had no experience either, meaning accidents and inefficiency would likely drown the invasion force before it even hit England.
3. The Germans needed five things for a successful invasion:
A) Win Air supremacy over the channel and at least air superiority over Britain itself. This was already impossible because the RAF was better, closer to home, and could build planes faster than the Luftwaffe.
B) Secure a mine free channel.
C) Somehow beat back the Royal Navy.
D) Build more ships than is possible under the German war economy to even ship over the men and supply needed to sustain an invasion force. Also invent a totally new landing craft in like two weeks.
E) Even if all those are somehow accomplished, then the German land forces have to actually beat the British land forces, who escaped at Dunkirk. The Germans biggest strength was its ability to surprise its enemy, there would be no such surprise here.
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