GHQ Operational Instructions No 1 (Jun 5th 1940) and No 3 (Jun 15th) detailed the revised policy of defence. The probable area of invasion was from The Wash to Newhaven with the possibility of strong diversionary raids on Shetland, Ireland (followed by an attack on the West Coast) and the North of England. Operational Order No 3 prioritized the immediate threat only – the coast between Lands End and Newcastle upon Tyne.
German tactics were expected to be the same as used in France. Armoured columns could be expected to push on regardless of support and flank protection. An armoured formation landed on a beach could function as a unit almost immediately. Infantry on the other hand would have to wait until transport and guns were unloaded before they could become mobile. The main danger therefore came from the armoured fighting vehicles. The German objectives were considered to be London and the Centers of Production and Supply in the Midlands the North.
The policy of defence to be adapted was a combination of offensive mobile columns and static defence by means of strong points and “stops”. As mobile columns could not operate over the whole area threatened by invasion, measures would be required to limit enemy movement until the mobile reserves could arrive for counter-attack. This would be done by a system of strong points and “stops” distributed in depth to cover London and the Centers of Production and Supply –to “prevent the enemy running riot and tearing the guts out of the country” as happened in France and Belgium.
The Coastal Areas were to be regarded as an outpost zone (often referred to as “The Coastal Crust”), to give warning of an attack and to delay and break up the initial attack. Selected beaches were in the process of being given 6” Naval guns in order to engage transports attempting to land troops. These guns, along with beaches most suitable for tank landings, would be defended by light machine guns in pillboxes, anti-tank blocks and anti-tank mines on the beach exits. Some improvised anti-tank guns would be provided (including a fleet of 76 lorries established which mounted a selection of obsolete 3 pounder, 6 pounder, 12 pounder and 4 inch guns) but the mine was to be the main anti-tank defence. However the majority of available field guns (786 in all by mid-June) would be sited for beach defence. The beach defence would be backed up by strong points in the rear.
Inland areas were to be divided into zones consisting of a series of “stops” cumulating in the GHQ Zone of Stops (also known as the GHQ Stop Line) which would be sited to cover London and the main industrial centers. These “stops” were to consist of defences of anti-tank obstacles, pillboxes, wire and static anti-tank guns. The bulk of available 2 pounder anti-tank guns (167 in all by mid-June) were to be placed in these “stops” rather than used for beach defence. Five of these “stops” lay across East Anglia to check advances inland (either towards London or towards the Midlands) from a force landed in the vicinity of Lowestoft and three crossed Kent, Sussex and Surrey to cover London from the South and South-east.
Above: Proposed GHQ Zone of Stops - the GHQ Anti-tank Stop line. In reality little work was done on the
line in the area of Northern Command and no work at all in the area of Scottish Command.
“Stops” were to be of two types:
1. Waterways and other natural obstacles such as steep hills. As waterways provided an effective obstacle it was intended to hold these lightly in order to concentrate forces for the remainder, weaker stops. Waterways were to be made into Demolition Belts by preparing bridges and crossings for demolition. Waterways at right angle to the main line of enemy advance were of the greatest value as they would hinder lateral movement of the attack and were to always be included in Demolition Schemes.
2. Where no waterways existed the “stop” was to be organized in great depth. It was to consist of an artificial obstacle (ditch or minefield) covered by pillboxes and the bulk of the remaining anti-tank guns.
Mobile reserves were to be held behind the GHQ Stop Line, ready to be deployed once the enemy attack had been delayed and canalized. In reserve was the 1st Armoured Division (although under half strength) and three of the better equipped infantry divisions dispersed in the area Aldershot-North London-Northampton so as to be able to act as independent mobile brigade groups. In addition the 2nd Armoured Division was located in the Northampton-Newmarket area, equipped with 178 light tanks so as to be able to operate against the flank or rear of any enemy troops landed in East Anglia or north of The Wash. C.I.C Home Forces (General E Ironside) considered there was little value in keeping large local reserves near the coast for counter-attack as the beach defence Divisions were still lacking in weapons and training which he considered would give little chance of success of any locally organized counter-attack.
The LDV were to keep a lookout for parachutists, Fifth Columnists and man certain road blocks. Anti-Aircraft defences (batteries and searchlights) were also to form anti-parachute parties and to place themselves under the order of local military commanders if they could no longer perform their A.A role.
Although the War Cabinet agreed that ”the plan of defence……appears to be generally sound” there were some reservations. The main concern was that not enough emphasis was placed on hitting the enemy hard during the most vital phase when he would be at his most vulnerable i.e. during disembarkation. While recognizing that some mobile reserves needed to be kept some distance in land in order to have space for deployment it was felt there was also a need for some reserves to be able to counter-attack immediately. The location of reserves in Ironside’s plan would take an unduly long time to deploy for counter attack on the coastal zone. Churchill agreed with these concerns. He thought that the idea of the First War German Stormtroops should be copied – a force of at least 20,000 specially trained troops who could deploy against any enemy landings within four hours (Churchill referred to these as “leopard Brigades”).
Ironside’s response to this was that mobile reserves had to be kept inland due to the need to deal with airborne landings as well as seaborne landings. He expected one main landing by air and up to three by sea with the enemy exploiting which ever was the most successful. He argued that four armoured divisions in reserve would secure the security of the country (but in reality he had less than the strength of half of one armoured division). Although the beach Divisions only had their Bren carriers as a small mobile reserve, the higher formations had some reserves as well as the main GHQ reserve that could reach the beaches much quicker.
Criticism on the plan continued to grow. In the opinion of the Vice-Chiefs of staff, allowing the coast to be held as an outpost line only and having the main line of resistance inland after a fair proportion of the country had been overrun was nothing but suicidal: "it appears that the main resistance might only be offered after the enemy had overrun nearly half of the country, and obtained possession of aerodromes and other vital facilities". It was also considered that Ironside had not pursued the creation of mobile reserves strongly enough, which the entire plan relied upon. Due to the haste of the situation, many of the road blocks were of no value as the enemy could just go around them and many pillboxes were built facing the wrong way. The “stop” lines were also regarded as series of linear unsupported defence positions. This was never Ironside’s intention. He emphasized that the principals of Field Service Regulations still held true (although modified) and at the time recognized that there was insufficient troops to man the positions but considered that the work should commence immediately while Britain rearmed (with Germany’s inactivity resources were increasing all the time in terms of both manpower as a result of conscription with 400,000 men expected to join the army in the following two months and also in weapons as factories worked day and night shifts).
Ironside was replaced by General Alan Brooke on July 20th and the concept of static defence and “stop” lines was more or less abandoned.
Defence Plans for the United Kingdom, TNA
Cabinet papers, TNA
Ironside's Line, Colin Alexander, Historic Military press, 1998