I’m reading the third and last volume of William Manchester’s biography of Winston Churchill.  Manchester passed away before it could be completed, but he talked Paul Reid into finishing it for him.  We are much the richer because he did.

Reid points out four reasons that Churchill felt Hitler would fail if he tried to invade Britain:

1. Not enough shipping to support it.  The first wave of 60 to 80,000 troops would require fully 60% of all German merchant shipping.  Where would shipping come to support the next wave of 160,000?
2. Not enough landing craft.  Germany did not have nearly enough landing craft to offload the tanks and artillery required to invade Britain.  The only alternative?  Capture a port and offload at the docks.  Britain’s response?  Mine the harbors.  Destroy port facilities if Germany tried to invade.  Rain down artillery fire from the surrounding area if they did try to use a port for invasion.
3. RAF resistance. Sure the RAF was outnumbered 3 to 1, but Churchill knew they would be fighting for their homeland.  Churchill’s conclusion?  Advantage Britain.
4. Sea power. The Royal Navy was much stronger than the German Navy.  Germany would have to attempt to destroy the much larger force using air power.

Sure if there were only one or two of these problems, the possibility of a German invasion was much higher.  Germany would have to overcome all four problems in order to invade, a difficulty with which the German Wehrmacht was fully aware.  The invasion would never come.  Hitler would turn his eyes towards Russia and Africa, and the rest is history.  Britain would survive.  Hitler would make the fatal mistake of trying to invade Russia.  Five years later he would be dead and Germany would be in ruins.