So much of the London WWII underground military command center–I forget its proper name–is chilling, but where I was hit to the gut was a map (the only one?) in Churchill’s sleeping chamber, of a map of the English coastline with possible German invasion sites mapped. Bottom line.
What in fact was in place in-country for that eventuality, before the invasion of Russia, when I believe an assault on England was most dangerous, and afterwards, as more time could be given to preparation?
Pre planned military battle commands? Plans for civil defense, including active battle by civilians, if necessary, with weapons depots, distribution plans, and a civilian para-command hierarchy? Food and fuel distribution plans? Martial law preparation by legal folk?
These are just a few I’ve thought of. I know it’s a big question.
If you go to the Southern coast of England today it isn’t difficult to find defensive WII defensive fortifications. More difficult to find, unless you know where to look, are the pillboxes deep inland in Southern England which formed part of the GHQ line, but there’s still plenty of them about in remote locations in woodlands and in the countryside.
Defense against an invasion was the responsibility of the Home Guard (aka “Dad’s Army”), but there resources were very limited as Britain had little to spare. There were elite Home Guard units who were trained in guerrilla warfare
The main British plan was to make sure to stay on the opposite side of a large body of water from Germany.
The UK had a smaller population than Germany to start with (48,000,000 vs 70,000,000). Most prewar British military development had been put into the navy and air force (France and other continental powers were expected to supply the bulk of the ground forces). And the British Army had lost a lot of troops and almost all of its equipment in the Battle of France.
So the British government realized it had no realistic chance of defeating the German military in a land battle anytime between the Summer of 1940 and the Summer of 1941. Their main strategy was to make sure such a battle wasn’t fought.
The government did make plans for fighting the Germans in Britain but these were mostly done for the purposes of keeping up public morale.
The most important was still to keep the factories running and the sea lanes open. Just after Dunkirk, the UK had only 3 divisions in England equipped to fight. Three months later, they had equipped 16 divisions with spanking new weapons. No more invasion of any kind was feared.
David Lampe’s The Last Ditch is well worth a read. Planning for a British Resistance movement was surprisingly extensive, and quite a few preparations were made.
If you have Google Earth then check out the Defence of Britain overlay. Warning: it takes an age to load as there are many thousands of sites detailed in it.
On a basic level, there are still thousands of these all around the coast, either in lines or more formidable formations; they were once at every conceivable place a landing could be made.
It wasn’t just the south coast; I clicked on one image of tank traps and it said ‘Caithness’, which is part of the very north of Scotland.
Or these (with panels slotted between them all) protected a shallow tidal access to the Forth and Rosyth Naval Dockyard; the main channel had submarine nets strung across.
The main wiki article on British anti-invasion preparationsis pretty good. It covers the changes through time from the crisis immediately following Dunkirk, through the frantic preparations between June and October (when the worsening weather ruled out a seaborne landing), to Spring 1941 by which time the British Army was in a much better condition. Post-Barbarossa there was never any likelihood of a full scale invasion although raids were always seen as possible and defenses went on being improved.
The article covers most of the points asked in the OP: the changing militiary planning from fixed lines to mobile reserves; the formation and role of the Home Guard, and (as others have mentioned) the linked, stay-behind Auxilliary Units. It mentions the pre-planning by local authorities with the military to identify resources and prepare for the worst. On Martial Law, the Defense Regulations under the Emergncy Powers (Defence) Acts of 1939 and 40 gave the government sweeping powers to regulate practically anything needed to prosecute the war effectively.
Incidently, the offices below Whitehall containing Churchill’s bedroom are properly known as the Cabinet War Rooms.
The whole country was covered by “Stop lines” defense lines where the Germans were expected to be halted for as long as possible. “Dads army” maybe a humerus thing to us now but they were expected to defend every bridge every cross road to the death. This was to holdup the attack for six days, by which time the UK fleet was expected to be in the channel having orders to steam full speed through mine fields to mince up the cross channel supply routs etc. A “war game” held at Sandhurst after the war employing many enemy commanders ended in German defeat/withdrawal with huge casualties.
I think the basic idea was to use any and every means possible to delay the Germans’ advance towards London long enough for the Royal Navy to arrive and cut off their cross-channel supply lines.
The plan, such as it was, was heavily criticised even at the time for allowing large portions of Southern England to be overrun before the decisive land battle would be fought, and in hindsight probably would have spelt the doom of England.
Hereis a link to a thread on the Axis history forum about the Germans’ intended use of paratroops in Operation Sealion. Specifically, the plans for the 7th Flieger division to take Lympne airfield on the southern English coast. It is an excellent thread where posters use google earth imagery to show where the proposed drop points were, the difficulties the terrain around the particular objective, the location of defence points, and the units that were stationed in the area. Of particular note, the paratroopers would have been dropping right into an area that had a unit specifically tasked with searching for and destroying paratroopers. The whole scenario is eerily similar to the later Market Garden debacle.
