An Air Staff memorandum (July 30th 1940) on seaborne invasion reasoned that Germany would have to gain air supremacy in order to secure her lines of sea communication. With the invasion of France, Germany could now concentrate her whole air force against Britain. Consequently it assumed (correctly as events soon proved) that the first phase of any invasion attempt would be a large scale air offensive against fighter aerodromes and organization and factories. It was also probable that Germany may attempt to weaken the Navy by attacks on naval bases on the East and South-east coasts.
In this first phase of operations the role of the Bomber Command was to carry out attacks on strategic targets within Germany to reduce the scale of air attacks on Britain. If reconnaissance revealed concentrations of shipping at ports and aircraft at aerodromes likely to be used for invasion, it was to immediately divert effort to attack these targets. While the main focus in 1940 was fighter production, a strong counter-offensive force of bomber aircraft had been maintained to reduce the scale of the expected air offensive at its source. By August Bomber Command had 613 first line aircraft spread over 25 operational stations. Throughout the summer of 1940 Bomber Command carried out raids against Germany and her occupied territories, targets including aircraft factories, aerodromes, railway junctions, petroleum installations and shipping. Incendiary attacks were made on German forests in August and September. During August, six Blenheims from Bomber Command carried out sweeps in the North Sea.
Right: Wellington Heavy Bombers, Mildenhall - Suffolk. With a
range of 3,200 miles these bombers made repeated bombing
attacks into Germany in order to reduce the air offensive at its
Should Germany decide to launch a seaborne invasion to defeat Britain, the invasion would be in three phases:
I Concentration of troops and shipping at points of departure
II The voyage from continental coasts to the British coast
III The establishment of a bridge head in Britain.
Role of Bomber Command was to attack the ports where the invasion fleet was assembling with the objective of destroying the enemy transports. The main focus of Bomber Command in the first weeks of September was Anti-invasion attacks against shipping, dock installations and barges. Successful attacks were carried out against Calais, Dunkirk, Ostend, Boulogne, Bremen, Hamburg and others on the nights of 8th/9th and 9th/10th with one bomber claiming six direct hits against a concentration of 60 large barges in Ostend Basin. Successful attacks were also carried out against barges on the night 11th/12th at Calais, Ostend and Flushing. On the night 10th/11th, bombers dropped flares assisting a destroyer attack off Ostend against three barges being towed by a trawler along with a merchant vessel. Germany estimated her losses to transports and barges between the end of August and end of September at embarkation ports to be 12%.
Role of Bomber Command was to attack the invasion flotillas with bombs and machine guns.
Role of Bomber Command was to attack the enemy transports with bombs and machine guns as they approached the coast. At a later stage to attack enemy forces and equipment that may have successfully landed.
The selection of bomb to be used in Phase I and II was important. To destroy enemy destroyers G.P bombs fused at 1/40th delay were considered best and against capital ships A.P or S.A.P bombs. When attacking invasion ports G.P bombs were considered better as targets would be many barges and wharfs with supplies etc – S.A.P / A.P would just bury themselves with camouflet effect and little useful results. The Admiralty considered the best bomb to use against barges and E boats was a G.P bomb fused to detonate a foot or so above the water. The Admiralty recognized that if using such a bomb against barge concentrations little effect would be obtained against other vessels.
If enemy forces succeeded in landing arrangements were put in place for co-operation with the C.I.C Home Forces. In June C.I.C Home Forces would exercise control of 50% of available medium bombers (this represented seven squadrons from No 2 Group and two squadrons from No 1 Group) and would be able to call upon them without reference to anyone. This arrangement was changed in August when all bomber squadrons acting in support of the Army would be centralized under GHQ and operated under control of C.I.C Bomber Command. Army commanders were to contact GHQ with targets to be engaged. An exception to this was if the invasion came as a surprise (i.e. before a state of readiness had been ordered with the expectation of invasion occurring within the next 12 hours). In this case an Army commander whose area had been attacked could apply direct to bomber squadrons as soon as he had a suitable target. In such a case Northern Command would request support from No 1 Group and Eastern, Southern and Western Command from No 2 Group.
If the situation demanded it, the Air Ministry would reinforce Bomber Command with aircraft at Flying Training Commands (under “Banquet” Training scheme), from O.T.U’s (under “Banquet 6” and “Banquet 7” schemes) and Lysander’s from No 22 Group* (under “Banquet 22 Group” scheme). These aircraft would be used to replace wastage in the front line.
The characteristics of Blenheim medium bombers and the likely conditions of their deployment were highlighted in a memorandum. As bombers were often likened to long range artillery the memorandum highlighted some decisive differences:
Bombers could never achieve the same intensity of fire over a period of time as artillery
Each bomber sortie had to take an independent aim
Bombers could never achieve the accuracy of artillery
“Fire” from bombers could never be brought down with the same speed as artillery.
The bomber could also not be expected to distinguish between friend and foe. As the wireless operator in Blenheims was also the gunner, it would be impossible to contact the aircraft when in action as he would be at his gun.
It was assumed that bombers operating in support of the Army would be without fighter cover. Under these conditions bombers would have to fly in formations of six or seven, even up to 12, in conditions of not more than half cloud – they would not be able to break formation for bombing runs hence bombs would be dropped over a wide area. In conditions of cloud cover they would have to operate singly as close formation flying was not possible and they would require very detailed instructions to achieve accurate bombing.
The Blenheim dropped its bombs from level flight or in a shallow dive. Bombs were normally dropped in an equally spaced line to ensure that at least one hit is achieved. Bombers could not be relied upon to hit pin-point targets. Experience in the Battle of France showed that despite many attacks against enemy armoured formations, little success was achieved. Most attacks were against the leading formations which were too widely spaced to cause serious damage and any blockage caused could simply be by-passed. The most successful attacks were against formations canalized and constricted by defiles.
The conclusion of this memorandum was that Blenheims were not suitable for close support but could offer good direct support against the right targets. Any enemy formations that succeed in advancing inland would require reinforcements, fuel and ammunition supplies. These would have to be landed at a few suitable points and stored – these points and the storage dumps were the points that the Blenheim could most effectively be deployed against.
Above: The Blenhiem Medium Bomber - this would be the main bomber used in support of the Army in the event
*No 22 Group was under the general control of C.I.C Home Forces. These Army Co-operation Squadrons were allocated to Army Commands and Corps. They were for all types of reconnaissance landward of the high water line and up to visibility distance seawards. Other roles would include spotting for artillery, attacking troops, message dropping and picking up and dropping supplies. The Lysander was ideal for this role as it could operate from small fields, had a top speed of 230 mph but could fly as slow as 50mph essential for dropping supplies and operating from small fields / hastily prepared runways.
Defence Plans for the United Kingdom, TNA
Invasion Memoranda , Air Ministry, TNA
Employment of Bomber squadrons in support of land forces in the event of invasion, Air Ministry, TNA
Cabinet papers, TNA
Britain’s Wonderful Fighting Forces, Odhams Press Ltd,