Could Britain have defended against an invasion in September 1940?

No they never returned. Not u8ntil D day

 

This is an excellent point. The German Navy of 1938 consisted of 75,000 men, according to 'Janes Fighting Ships', and there was no organization similar to the RNR or RNVR available to permit rapid expansion..

Manpower was found by using personnel from ships under repair, new ships in the later stages of construction, and by laying up some vessels, notably the ancient battleships Schleswig-Holstein & Schliesen.

This produced some 4000 men, and appeals were then made for men with appropriate experience. In this case, 'appropriate experience' apparently included an interest in boating or canoeing.

In addition, some bargees from occupied countries were also 'volunteered.'

I leave you to decide whether an interest in canoeing could be considered sufficient experience to take a vessel of uncertain seaworthiness across the Channel, not once but numerous times over a period of several weeks, at a time of year when there was every possiblity of deteriorating weather and worsening sea states.

I have my own view on the matter!
There also is the point that the speed of the berges was lower than the east west current of the Channel.

 

Pill boxes and static defences even in depth use up vast resources to man and supply. If the enemy intends to attack with all of his forces then all of the static defences would be engaging, to get a large army ashore and move inland congestion would be the enemy. More likely a local concentrated attack to get a bridgehead established and fight in and outwards to protect your flanks as you surge inland and your forces secure the supply lines. The home forces need mobile reserves who can move to any landing and use the restricted area on the landing ground as the killing zone. I believe Montgomery and others were not happy with static defences, the first of the Auchinleck -Montgomery arguments if memory serves me.

 

Pill boxes and static defences even in depth use up vast resources to man and supply. If the enemy intends to attack with all of his forces then all of the static defences would be engaging, to get a large army ashore and move inland congestion would be the enemy. More likely a local concentrated attack to get a bridgehead established and fight in and outwards to protect your flanks as you surge inland and your forces secure the supply lines. The home forces need mobile reserves who can move to any landing and use the restricted area on the landing ground as the killing zone. I believe Montgomery and others were not happy with static defences, the first of the Auchinleck -Montgomery arguments if memory serves me.

Monty and Auk had been clashing since their days at staff college. But I'm not sure I follow your argument regarding static defences. They do consume resources both in terms of equipment and manpower whilst under construction but once built they act as a force multiplier, especially as they can be effectively manned by poorly trained or relatively unfit troops. See the problems that the US Army had when trying to break through the Westwall during late 1944 and early 1945 - the men holding most of the strongpoints were either old men or boys. Ironside, Brooke, Auchinleck and Montgomery did not believe that static defences could stop an invasion, only slow it and cause losses. They were concentrated in those areas where the invasion was expected to take place and along the likely lines of penetration once the Germans were ashore. The real disputes were over when and where to counter-attack. Ironside believed in allowing the Germans to advance to the GHQ Line where the bulk of the Imperial forces would engage them in a decisive battle. Brooke and Montgomery, both of whom had experience of fighting the Germans in France, wanted to hit them hard and early, even at the risk of not having the full complement of the Imperial forces behind them, to exploit the probable disorganisation of the Germans when they landed. There is some logic in both approaches and each has its own set of risks. Fortunately neither theory was put to the test.

 

Had Hitler invaded shortly after Dunkirk he might just have made it, but the construction and speed of the defences that were built after Dunkirk was some thing else.

Indeed. What sometimes goes missing when discussing that possibility is that the Heer and the Luftwaffe had taken heavy losses during the French campaign. Not only that but there were maintenance issues to deal with and the establishment of proper air bases in Northern France and Belgium. Fortunately for the British German factories weren't churning out replacement aircraft, tanks, guns and bullets at a rate to make good their losses let alone establish a substantial reserve of spare equipment.

 

... and appeals were then made for men with appropriate experience. In this case, 'appropriate experience' apparently included an interest in boating or canoeing.

You will surely admit it would provide for an intense even if short sensation

 

You will surely admit it would provide for an intense even if short sensation
A definitely interesting experience Za. Maybe it might totally confuse the Royal Navy having thousands of kriegsmarine using canoes, very cunning! Everyone expecting an airborne invasion and they arrive in canoes!!!

 

Static defences of the type built in the UK were not really there to stop the enemy, they were there to slow down, break up an advance and channel forces.

The strong points slow down an attacker by forcing them to deploy heavier weapons, if by passed they have to leave men behind to watch them.
They break up the advance by slowing down one part while others where there are no defences can still advance at full speed. This it is hoped allows you to counter attack from the flanks or take on the enemy piecemeal.
They are used to channel forces into 'fire zones', pre-registered artillery zones, supported by maybe large local counter attack forces. To make best use of a limited number of troops so you can overwhelm at the point of contact. This is especially true of minefields where you do not have enough to cover a whole front (mix of real and dummy minefields)

If you look at them that way they were cheap in cost to make and manpower.

They were never intended to be a Maginot line type defence.

 

The defences built along the coast were built to stop the enemy. Pill boxes by the thousands were built along with gun emplacements, miles upon mile of barb wire was strung, mine fields all along the coast, then to top this of many of the beaches that could have been used by the Germans along the south coast to bring in the barges had fire walls installed and if they where turned on the sea could be turned into a wall of fire. Had you been around at the time you would have had a good idea that this was stop them getting ashore and any that made it would have walked into a firestorm of bullets and other nasties. The other thing to remember is that a lot of the South Coast is made up of very high cliffs and landing sites were limited and well covered

 

I will admit I have limited knowledge of the defences having had more lectures about the inland defences and stop lines and how they relate to the way the RE would use field defences and minefields nowadays (Early 1980's to the mid 2000's)

I suppose it comes down to who was in charge as to what they would be expected to do where they were strong. Either stop and destroy the enemy there and then or to hold them up long enough for the reserves further back to move to the area and launch the final blow.

I believe Rundstedt and Rommel had a little disagreement about this sort of thing.

 

Leccy and Tab - you need to take a look at David Newbold's PHD (War Studies) thesis BRITISH PLANNING AND PREPARATIONS TO RESIST INVASION ON LAND, SEPTEMBER 1939 - SEPTEMBER 1940, it's in the British Library ETHOS collection but you can join via the Net for free and the thesis is downloadable free. It's an essential read for the TRUE state of British defences.

Things were both more rosy in some ways....and yet at the same time far less rosy than you might have imagined.

 

Thanks very much for that, downloading now.

 

Indeed. What sometimes goes missing when discussing that possibility is that the Heer and the Luftwaffe had taken heavy losses during the French campaign. Not only that but there were maintenance issues to deal with and the establishment of proper air bases in Northern France and Belgium. Fortunately for the British German factories weren't churning out replacement aircraft, tanks, guns and bullets at a rate to make good their losses let alone establish a substantial reserve of spare equipment.

I think General Blumentritt suggested that an immediate invasion hot on the heels of Dunkirk might have succeeded.

However, aside from the relevant points you have already made, Blumentritt was clearly unaware of the fact that the Kreigsmarine had almost literally no ships available to make this possible. The British left almost nothing in the way of merchant shipping from the Germans to commandeer.

As an example, as early as 15 May, the destroyer Brilliant led a task force into Antwerp and 'liberated' 26 merchantmen, 50 tugs, and around 600 barges from Antwerp.

By contrast, at a meeting with Hitler, Keitel and Jodl on 20 June, Raeder estimated that the Kriegsmarine could make 45 barges available within two weeks.

 

An early July invasion is Kenneth Macksey's posit for his 1970s book on Sealion - he doesn't argue the PODs well, but he was pretty good for the day for a snapshot of British defences, German mustering of artillery etc.

It was the first place where many years ago I came across the (rapidly abandoned!) idea of grounding the Schleswig-Holstein and Schlesien just offshore as armoured gun emplacements to provide artillery support...whatever else you can say about their preparations, the Germans knew when to abandon REALLY bad ideas!

 

I think General Blumentritt suggested that an immediate invasion hot on the heels of Dunkirk might have succeeded.

However, aside from the relevant points you have already made, Blumentritt was clearly unaware of the fact that the Kreigsmarine had almost literally no ships available to make this possible. The British left almost nothing in the way of merchant shipping from the Germans to commandeer.

As an example, as early as 15 May, the destroyer Brilliant led a task force into Antwerp and 'liberated' 26 merchantmen, 50 tugs, and around 600 barges from Antwerp.

By contrast, at a meeting with Hitler, Keitel and Jodl on 20 June, Raeder estimated that the Kriegsmarine could make 45 barges available within two weeks.
Hm,Antwerp was captured by the Germans on 18 may only .

 

...but the locals mightn't have been too happy about it either! I presume it was part of the "XD Operations", a series of "denial ops" that removed various strategic resources - both static and "mobile" - from the path of the advancing Germans. From Wiki...

In May 1940, the German Army invaded the Netherlands and Belgium. The British military authorities were determined that the large oil installations at the major ports should not fall into enemy hands. The KFRE were despatched in secrecy on 11 May to Amsterdam to negotiate with the local commanders and destroy the installations and the large oil stocks and assist with dockyard demolitions; these were called "XD Operations". They were successful in spite of the lack of advance planning and specialised equipment. After Amsterdam, detachments carried out more oil demolitions at Rotterdam and Antwerp, and assisted with the evacuation of 40 tons of Dutch gold from Rotterdam. At times they exchanged fire with German advance patrols.

 

How were they to man these as I have read that the Kreigsmarine itself said it would need to find 20000 men to man these vessels. By stripping training units and paring down the surface fleets manning they could produce 16000 leaving a shortfall of 4000. Baring in mind the effect that stripping crews from other vessels would have on their ability to do the jobs required.

The number of barges actually assembled for 'Sealion' is, in point of fact, much less important that the fact that the Germans were always short of tugs.

As even powered barges could not cross unaided, the German intention was for a tug (or more likely, a trawler as tugs were scarce) to tow barges in pairs, usually consisting of a powered barge followed by an unpowered one.

The plan for the initial landings required 894 barges, towed by 390 tug/trawlers and 57 freighters, together with 300 motor-boats. According the Walter Ansel (an American Admiral who worked on the planning for D-Day, and subsequently wrote 'Hitler Confronts England' - an account of Operation Sealion based on discussions with surviving German naval officers who worked on it, together with access to Kriegsmarine archives) at the end of September, the German had only 397 tugs available.

There was, therefore, absolutely no margin for error, and even if everything went well, at the end of the first day the Germans could have transported, at most 59,000 men to Britain, in bridgeheads which were too separated to support each other, and without their divisional artillery or most of their wheeled transport, although with thousands of horses.

By 'if everything went well' I mean firstly, that the weather remained calm, and secondly that the Royal Navy did not interfere! To given an idea of the size of the barge formations, the biggest, from Boulogne, would have involved four parallel columns of tug/barge combinations, each column being forty combinations long, and the formation from Calais would have been, according to the commander, Captain Kleikamp, 16.5 kilometers long.

The Royal Navy carried out nightly patrols in September, 1940, and I would submit that it is rather unlikely that they would have missed these formations. Once they were reported some 70 destroyers and cruisers, plus several hundred patrol vessels, all based between Plymouth & the Nore, would be despatched. By the way, despite claims by the odd member of the 'Sealion Appreciation Society' that the RN had few vessels in the Channel area, these vessels really were where history says they were!

The point to consider is, once the Royal Navy had finished with them, how many of the tugs, let alone the barges, would still have been operational, or even afloat.

The fact is, in the absence of proper transports, the Germans were trying to make do with vessels wholly unsuited for the task, and vessels which, moreover, were not even capable of crossing the Channel unaided. Having a surplus of a thousand or so barges is not much use if they can't go anywhere.

I leave it to those reading this post to judge for themselves the validity of the points I have made.