By July 1941 it was evident that Germany was fully committed to a major campaign in Russia with almost her entire front line force deployed. The continued resistance offered by the Russians led the Chiefs of Staff to conclude that an invasion of Britain would be postponed and unlikely before the winter. In August 1941 the Commander In Chief produced an appreciation of the minimum forces needed by spring 1942 to defeat any invasion.
This appreciation made a number of assumptions:
Firstly that the nature of the attack would change. It was noted Germany’s war production was focused on ground force troops for the operations in Russia at the expense of her air force. In contrast the RAF had expanded greatly. Therefore any attack would not be preceded by a large scale battle for air supremacy. Instead any attack would be a combined land, air and sea operation concentrated in a surprise attack, with speed and rapid exploitation of success.
Secondly it was assumed that Germany would not quickly be able to disengage from the Eastern Front – a minimum of one months notice was expected of any invasion attempt.
The Admiralty worked out a programme where two thirds of the destroyers and 75% of other coastal vessels in Home Commands could be deployed to anti-invasion duties in three weeks. However they considered that actual conformation of the invasion would be required to divert ships to anti-invasion duties due to the demands on protecting the various convoy routes. This might lead to delay of five to seven days after an invasion had started before the Navy in Home Waters could be employed on anti-invasion duties.
The Air Ministry maintained that an invasion would not occur until Germany had defeated Britain’s fighter force. The C.I.C Home Forces however maintained that the defeat of Fighter Command was not necessary before German troops could be landed. The C.I.C believed not enough consideration had been given to the potential lack of naval support in the first few days or of the risk that Germany may be prepared to take to force a decision. He also considered that given the large number of ports available to Germany, Bomber Command could not disorganize / disintegrate an invasion force of up to 40 divisions before it sailed or prevent it from landing in this country.
The German plan was expected to be a pincer movement on London. The importance of Kent was highlighted by the Chiefs of Staff as being the only place where Germany would be able to secure initial lines of communication by mounting guns or using captured British guns and deny the Straights of Dover to British Naval forces. Further forces were expected to land on East Anglian beaches with a pincer movement from these beaches and Kent on or to the west of London.
Given a level of German success in Russia by the spring of 1942 which would be sufficient to withdraw all troops except for those required for security arrangements, it was assumed the maximum strength available would be concentrated for an attack on Britain. Troops were not in short supply (Germany had some 20 Armoured and 250 Infantry divisions) but shipping would be the limiting factor. Germany had an estimated 3,000 self propelled barges, 1,000 merchant vessels totaling two million tons, about 2,000 unconverted barges and between 450 to 800 special tank landing craft.
The probable landing areas (and anticipated troop numbers) were expected to be the beaches of East Anglia (three Armoured and nine Infantry divisions), Kent and Sussex beaches (four Armoured and 11 Infantry divisions) and a diversionary force on beaches east of Weymouth (two Armoured and three Infantry divisions). It was expected the Germans would suffer 50% casualties in any landing still leaving a substantial force to deal with.
To counter this, the C.I.C Home Forces estimated he would need eight Armoured and 14 Infantry divisions as well as 12 lower establishment (County) divisions and 10 Army tank brigades. The Home Guard was expected to have reached strength of 1.5 million by the spring of 1942.
The first part of any invasion was expected to be the landing of tanks covered by special anti-aircraft barges with high velocity guns mounted on them. Their purpose would be to produce smoke screens and shoot up the concrete defences as well as anti-aircraft defence. By 1941 many 6 pounder and 4 inch guns had been deployed for beach defence but arrangements were also made to back these up with 3.7 inch anti-aircraft guns to act in an anti-tank role (Bargain Scheme).
The plan was still to hold the Coast as an outpost line. However the key beaches of Sussex and Kent were to be held with four Field Army divisions. The key to the defence was still rapid counter-offensive by mobile reserves, both local reserves (to counter attack against enemy forces that had overrun the beach defenses) and GHQ reserves (to counter attack against any forces that penetrated further inland). The intention was to deny the formation of a secure bridge head for enemy forces through which the main invasion force could be landed, supplied and maintained. The enemy was to be driven back into the sea as rapidly as possible and the training of armoured and field forces had been designed to that end. As soon as the main German landing areas were confirmed, reserves from other Commands would be moved to pre-arranged areas in the area of the threatened Command.
The best method of meeting the German system of infiltration was defence in depth and holding of nodal points and the lines of communication. Due to the short distance between the coast and London, all approaches to London had been prepared as tank proof localities with reserves based on these localities in order to be able to manouvere from a secure pivot.
As well as a seaborne attack, airborne attack was still a threat. By the spring of 1942 Germany was expected to have available 3,500 troop carrying aircraft capable of transporting 55,000 troops over three days. The main objectives of airborne troops were considered to be:
Attack on vital aerodromes and R.D.F stations
Landing in behind beach defences to attack them from the rear
An attack on London combined with a seaborne invasion force.
The main defence against airborne troops was firstly Fighter Command and the anti-aircraft guns. Mobile formations were also formed to deal with airborne landings – for example light tank units were stationed on the South Downs along the Medway crossings to deal with parachute troops who may try and seize these crossings to prevent reinforcement of the Sussex and Kent beaches.
Air defence Plan
The changed assumption of the German air attack i.e. the air battle would be fought in direct co-operation with a combined seaborne and airborne invasion required a drastic redeployment of air and anti-aircraft defences which would now have to be concentrated on a line south of Bristol – The wash to deal with an expected invasion on a line south-east of The Wash – Weymouth.
With ongoing operations in Russia, it was considered Germany only had 1,000 aircraft of all types in the West. With success in Russia, three months would probably be required to transfer the air strength to the West when the German air strength was estimated at 2,100 bombers and 1,520 fighters. Fighter Command’s minimum requirements were stated to be 75 day and 23 nig fighter squadrons. By Jan 1942 66 day and 25 night fighter squadrons were available (totaling 1,484 aircraft). To this could be added 120 aircraft from the Army Cooperation Squadrons and 800 training aircraft (Banquet Scheme). Fighter Command would probably have fighter superiority over the German fighter force.
Plans were made to transfer up to 1,000 heavy and 800 light anti-aircraft guns, widely distributed over Britain to the probable invasion area The Wash-Weymouth. Priority was to be given to the defence of aerodromes, RDF Stations and centers of communication (such as Canterbury, Ashford and Maidstone through which mobile counter attack reserves would have to pass through).
By Oct 1941 it was evident that the forces required by The C.I.C. Home Forces would not be available by the spring of 1942. The formation of armoured divisions was not proceeding to programme due the dispatch of tanks to the Middle East and Russia. It terms of infantry there was the need to take into account the constant demands for reinforcements in the Middle East. The Chiefs of Staff now questioned whether the scale of attack accepted by the C.I.C. still held good. They considered that not enough emphasis was put on the casualties that the air force would inflict on the Germans, especially now the balance of air power was in Britain’s favor. Churchill also considered that Bomber Command could now prevent the nearest Channel ports (Dunkirk, Calais and Boulogne) being used as invasion bases. He also questioned the number of barges estimated to be available to Germany.
As a result a the Chiefs of Staff set up an Inter-service Committee on Invasion –a ‘German Syndicate’ consisting of senior officers of all three services to consider themselves in the place of the German Staff. They considered that the invasion would be limited to the South-East coast unlike a pincer movement assumed by C.I.C Home Forces.
The actual dispositions of Home Forces in spring 1942 were considerably below the minimum level envisaged by the C.I.C Home Forces in Aug 1941. The strength of South-Eastern Command was maintained at the expense of other Commands.
Above: Left - The expected German Plan of invasion as drawn up by the
Inter-service Committee on Invasion. Right - the actual deployment of
Home Forces in Spring 1942
Defence Plans for the United Kingdom, TNA