During late autumn GHQ appraised the Home Defence situation against invasion. The anticipated scale of attack in the various Commands was estimated as follows:
It was anticipated that Germany now had access to sufficient aerodromes in the occupied countries to operate its entire air force against Britain, although a number of the runways did not have water proof surfaces so could only operate in dry weather.
It was also noted that invasion could occur in any season – the long dark nights of winter would give the enemy an opportunity to launch an invasion flotilla undetected but on the other hand rough seas often present during winter would preclude the use of barges and other small craft.
Home Forces available as at Nov 1940 to meet any invasion were given as:
Unbrigaded battalions were for the most part employed on the defence of aerodromes and vulnerable points.
The length of the Coast between Duncansby Head and Land’s End was 1,572 miles of which 485 miles were suitable to land a force of all arms and 187 miles for infantry only. It was noted that the length of beaches suitable to land a force of all arms exceeded the Western Front of the Great War, but it was realised that only the beaches of South-east England and those in the vicinity of ports needed to be held in strength (given Britain’s naval strength and the need for Germany to provide fighter aircraft cover for any seaborne invasion).
As well as the seaborne threat it was emphasised that account had to be taken of the airborne threat. It was considered that Germany may launch airborne attacks to reinforce a seaborne invasion or to gain aerodromes in order to extend the limit of her fighter cover. Airborne attacks could be anticipated on a line south of the Wash – Bristol Channel as well as within 20 miles of the ports of Hull, Middlesbrough, Newcastle and Edinburgh. It was anticipated that 78 battalions would be required to guard aerodromes as well as sufficient mobile forces for counter-attack.
If Germany undertook a seaborne invasion it was anticipated that she would seek a quick decision on land, and not rely on the securing of sea communications for more than a short period (with perhaps the exception being in the Narrow seas). The best chance of a quick success on land was with Armoured formations and the best method of dealing with these was with armoured divisions.
The plan for the defence of Britain in 1941 was to hold the most vulnerable parts of the Coast (Kent, Sussex and parts of East Anglia) with Field Army formations and the rest of the Coast with second class Beach Divisions and keeping the rest of the Field Army as a mobile reserve. The Field Army was increasingly withdrawn from static defence and trained in a mobile counter attack role. These formations were expected to be able to travel 150 -200 miles per day in motorised transport or march 20 – 40 miles on foot and be ready to deploy and fight on arrival.
The second class Beach Divisions were made up by grouping independent infantry brigades and other units into an operational formation with an administrative HQ – referred to as County Divisions (e.g. Devon and Cornwall Division). They had a lower establishment than Field Army divisions with little in the way of artillery or transport. It was planned to meet the deficiencies in artillery, transport, signals etc by the formation of new units. But until this was possible they were put together by drawing from Corps troops or converting other units (e.g. the conversion of Fortress Companies into R.E Companies). As well as replacing the Field Army formations withdrawn to form mobile reserves, these Beach Divisions also allowed the deployment of an increasing number of Field Army formations oversees, particularly to North Africa.
During February 1941 Eastern Command, which had practically included the whole likely invasion area from The Wash to Bognor Regis and was considered too large an area for a single Command, was split into two areas – Eastern and South-Eastern Command, roughly divided by the Thames Estuary and the London district.
During the Spring of 1941, invasion was considered less and less likely as the strength of the British Armed Forces increased. It was considered that it would be a gamble for Germany to undertake invasion – she was expected to force a conclusion of the war by other means, principally though blockade as the Battle of the Atlantic grew in ferocity.
The German Balkan Campaign which opened on April 9th 1941 and cumulated in the expenditure of a large number of trained parachute troops in the capture of Crete and the commencement of operations against Russia on June 22nd made invasion of Britain even less unlikely. On 31st July an assessment by the Chiefs of Staff considered that any invasion against Britain would be postponed until October 1941 at the earliest as Germany would need at least 6 to 8 weeks to disengage the large number of troops from the Eastern front required for any invasion attempt. Accordingly the C.-in C. Home Forces prepared an appreciation for the Defence of Britain during Spring 1942.
Above: Map of Home Forces, May 1941. Not shown above were three divisions (5th, 53rd and 63rd) and two brigades based in Northern Ireland and six battalions, two companies and one machine gun comapny based in the Orkneys and Shetlands.
Defence Plnas, TNA
Home Defence 1940, TNA