The Invasion Risk:
The Crisis and After
(September, 1940-June, 1941)
Disposition of Home Forces
11th September 1940
IN JULY and August, while German plans and preparations for invasion were moving towards the position shown in Map 13, British anti-invasion forces were doing their best to overcome the deficiencies so evident in May and June. By early September, Home Forces were stronger than in the summer, though still uncomfortably weak. About half the twenty-seven infantry divisions had had little collective training.1 Four divisions were fully equipped, eight fairly well equipped; the rest lacked much important gear, especially transport.2 Four light anti-aircraft batteries, with forty-eight guns, were ready to co-operate with the Field Army for defence against dive-bombing,3 but several times that number would not have been too many. Troops intended to serve as mobile brigade groups were of good quality, but lacked experience of Blitzkrieg tactics; and unrehearsed arrangements for bomber, fighter and training aircraft to share in a joint-service effort against the invader would doubtless have come up against many difficulties in practice.
Notwithstanding these deficiencies, the Field Army was considerably better off than in the early summer. Since the middle of June the number of field guns in service had increased substantially, 425 25-pounders having been added, of which 194 were new and the rest converted pieces.4 Two-pounder anti-tank guns had increased likewise from 176 in June to 498 at the end of August; and in early September the armoured units possessed some 240 medium and 108 cruiser tanks, all armed with two-pounders.5 Between midsummer and the early autumn the number of light tanks armed with machine-guns also increased threefold, rising from 178 in mid-June to 514 at the beginning of September.6 Against an enemy well equipped with armour, light tanks would, however, be of doubtful value.
In other respects good progress was made during the summer months. The Local Defence Volunteers, renamed the Home Guard on 31st July and now nearly half a million strong, had become by
September a valuable adjunct to Home Forces. Organised to fight in the neighbourhood of their homes, the volunteers provided a network of defended villages, parishes and townships which would hamper the consolidation of troops landed from the air in inland districts, and would reinforce the static defences near the coast. Afterwards mobile detachments equipped with motor-cars, motorcycles and bicycles were formed among the younger men. Meanwhile the process of strengthening and supplementing the coast defences, described in Chapter VIII, was in full swing, though the widespread system of fixed defences, local naval defences and minefields thought necessary since the fall of France was still some way from completion. To complement the extended East Coast mine-barrage, whose installation had been taken seriously in hand after the German occupation of the Dutch and Belgian seaboard and was finished in August, the Northern barrage from the Orkneys to the Faeroes was begun on 10th July, and the South-Western barrage from Cornwall to Eire on the 26th.7 (See Map 9.) New minefields off Northern Ireland were put in hand on nth September; meanwhile the Dover barrage was strengthened and local minefields were laid off South Coast ports.
The disposition of Home Forces in early September conformed generally to the revised plan drawn up in July.* The greater part of the mobile reserves were behind the sector from the Wash to New-haven, where a landing-force could be most easily covered by fighters working from Continental bases and would be on the shortest route to London. Elsewhere landings would have to be contained by local garrisons, which could expect no immediate assistance from the general reserve and would depend on the navy and air force to cut off reinforcements and supplies. The G.H.Q,. Reserve consisted of two corps north and south of London. Most of the IVth Corps, comprising the 2nd Armoured Division, the 42nd and 43rd Divisions and the 21st Infantry Brigade Group, straddled the border between the Home Counties and East Anglia; the VIIth Corps, comprising the 1st Armoured Division, the 1st Canadian Division and the 1st Army Tank Brigade, were in Surrey. To supplement the passing of orders by field telephone and General Post Office lines at the disposal of Home Forces, units had been issued with civilian wireless sets, and an army broadcasting station had been set up to disseminate authentic information and so counter false reports which might be spread by German agents. Despite the progress made in recent months, shortage of armour and inadequate experience of mobile warfare were still outstanding weaknesses.
Across the Channel the situation early in September was that all first-wave divisions had reached their assembly areas or would do so
* Map 17 shows the disposition of Home Forces on 11th September; Map 18 what the German High Command believed to be the position nine days later.
German Intelligence Map
by about the middle of the month. By 4th September 168 transports totalling 704,548 tons, 1,910 barges, 419 tugs (including trawlers) and 1,600 motor-boats had been requisitioned.8 Except in the case of tugs these numbers substantially exceeded the estimate of requirements made by the Naval Staff six weeks before.* The German Naval Staff expected the fleet to be ready by the 19th, but needed ten days' warning to do the necessary minesweeping and lay their own tactical minefields on the flanks of the cross-Channel route.9 In other words, if troops were to land in England on the 21st--the earliest day now contemplated--the Führer would have to give preliminary orders on the 11th.
In early September the Führer was still uncertain whether 'SEALION' should be carried out or not. Whatever may have been his opinion of the inherent value of the operation, he was in no position to give positive orders for its execution until a substantial victory had been gained over the opposing air force. But such a victory might itself lead to a situation which would make 'SEALION', with all its risks, unnecessary. When the 11th came he therefore renounced any intention of giving the preliminary order before the 14th.10 German air losses on the nth were smaller than those inflicted on Fighter Command; and after a quiet day on the 12th he announced on the 13th that, in view of the apparently hopeful but still uncertain situation in the air, the moment to launch 'SEALION' had not yet come.11 After a discussion with the heads of the three services next day he postponed the warning date for three more days, thereby abandoning any prospect of beginning the invasion before 27th September--incidentally the last day, until 8th October, when moon and tide would favour a landing.12
Meanwhile the Luftwaffe had taken steps calculated to ease the task of supporting a Channel crossing, but equally convenient for the next stage of an independent air offensive. Early in September Luftflotte 2 assumed command of Fliegerkorps VIII, a formation hitherto under Luftflotte 3 and responsible for a number of bomber and fighter units based in Normandy.13 Thereupon most of the dive-bomber units hitherto divided between the two Luftflotten were concentrated under Luftflotte 2 near the Straits of Dover. At the same time the two incomplete bomber Geschwader previously under Luftflotte 5 moved south from Norway and Denmark to Holland and Belgium, where they too came under Kesselring's command. Thus on the morning of the 7th--a day of crisis for the British High Command--nearly six hundred serviceable bombers and dive-bombers and some seven hundred fighters, besides reconnaissance and minelaying aircraft, were available to Kesselring either to continue the air war as an independent
* See p. 176.
operation, or to support a landing by the 16th Army if he were told to do so.* Further west, Sperrle could call similarly on some three hundred and fifty serviceable bombers and dive-bombers and about a hundred fighters, either for his own purposes or to support the 9th Army and, if necessary, the 6th Army also. By these moves the resources of General Stumpff in Scandinavia were reduced to a few reconnaissance and minelaying aircraft and some short-range fighters.
To sum up, by the middle of September the enemy's dispositions for the invasion of this country were either complete or on the threshold of completion. All he lacked to make invasion a reality was control of the intervening skies and waters, which alone could give him power to put the venture into execution if he chose to do so.
A great part of these arrangements was hidden from the British High Command by the proverbial fog of war. By the late summer the Prime Minister and Chiefs of Staff had ceased, indeed, to fear a landing in Scotland from Norwegian harbours, despite German,, efforts to create the impression that such a move was contemplated.14 But whether the enemy meant to come across the North Sea or across the Channel was not known, and his probable strength was at first equally uncertain. On the other hand, he could not sail without first assembling a mass of shipping which would not easily escape detection. Hence air photographs, supplemented by shrewd guesswork and time-honoured sources of intelligence, ultimately revealed the state of his preparations fairly clearly.
We have seen in Chapter VIII that up to the end of August the Combined Intelligence Committee--often aptly though inaccurately called the Counter-Invasion Committee--found no evidence that such preparations were well advanced. But the next few days brought a marked change. Frequent cover of the coastal strip from the Texel to Cherbourg showed a striking increase in the numbers of barges at ports between Ostend and Le Havre, the number at Ostend alone increasing from eighteen on 31st August (and none on the 28th) to two hundred and seventy on 7th September.15 During the same week many barges, motor-boats and larger vessels were seen or photographed moving westwards from the North Sea coast towards the Channel ports, where the arrival of most of them was subsequently confirmed by further photographs. At Flushing about a hundred barges were found on 4th September to have arrived since the beginning of the month; at Dunkirk and Calais substantial arrivals
* For details, see Appendix XVII.
Coastal Command Anti-Invasion Patrols
26th September 1940
were attested in the next two days.16 Thus by the morning of the 7th there was much evidence from reconnaissance alone to suggest that an early landing might be expected.17
Other indications which did not escape notice were the movement of Kampfgeschwader 26 and 30 to the Low Countries and the assembly of dive-bombers near the Straits.18 As if to clinch the matter, four Germans caught landing from a rowing-boat on the South-East Coast confessed that they were spies, whose task was to be ready at any time during the next fortnight to report movements of British reserve formations in the quadrilateral Oxford-Ipswich-London-Reading.19
Observing that conditions of moon and tide on the South-East Coast would particularly favour a landing between the 8th and 10th, the Joint Intelligence Committee (to whom the Combined Intelligence Committee reported) therefore informed the Chiefs of Staff on the 7th that invasion might be imminent.20
At a meeting which began at twenty minutes past five that afternoon the Chiefs of Staff agreed that imminent invasion had become a possibility.21 On looking into the states of readiness of the defence services they found that the navy had already put all small craft at immediate notice during the hours of darkness and at short notice by day. Thus the local naval commands were substantially ready to go into action without further warning. Short of bringing the Home Fleet southwards, nothing remained to be done where naval measures were concerned. The air force had already come to a state of readiness which envisaged a landing within three days; accordingly, twenty-four medium bombers stood constantly ready to co-operate with Home Forces at half an hour's notice, while half the remaining medium bombers had been earmarked for special tasks as soon as invasion was under way. The civil departments had received no special warning; in Home Forces troops 'stood to' daily at dawn and dusk and otherwise were at eight hours' notice. No provision had been made for any stage of readiness intermediate between eight hours' notice and 'immediate action'. After a discussion attended by Lieutenant-General B. C. T. Paget, Chief of Staff to General Brooke, the Chiefs of Staff took note that 'immediate action' would be ordered for troops in Eastern and Southern Commands.
Meanwhile the prospects of invasion were being studied at G.H.Q., Home Forces, in the light of the information available there. At seven minutes past eight that evening the signal 'CROMWELL' was issued from that headquarters to Eastern and Southern Commands, to all formations in the London area and to the IVth and VIIth Corps in G.H.Q. Reserve, which were thus brought to 'immediate action' by the only practicable method.*22 Other commands received
* General Brooke was absent on duty at the time; General Paget, as we have seen, attended the meetings of the Chiefs of Staff that afternoon. According to the recollection of General Paget's deputy, Brigadier (later Lieutenant-General Sir John) Swayne, Brigadier Swayne authorised the despatch of the signal on his own responsibility before the outcome of the meeting of the Chiefs of Staff was known to him and on the assumption that neither of his superiors was available for consultation.
the signal for information only. Thereupon forward divisions affected by the warning took up action stations. In some parts of the country certain Home Guard Commanders, acting on their own initiative, called out the Home Guard by the ringing of church bells, thereby giving the impression that German parachutists were already descending on the countryside.23 Amidst the prevailing atmosphere of expectancy reports were received that parachutists had actually landed and that fast German motor-boats were approaching the coast, but on investigation all were shown to be without foundation.24
Apart from these local excitements, reinforced by the solid reality of an air attack on London, the night passed peacefully enough. Next morning General Brooke made it clear that church bells were to be rung by order of a member of the Home Guard only if he had himself seen at least twenty-five parachutists descending, and not because other bells had been heard or on the strength of second-hand reports. He also explained that the code-word 'CROMWELL' was not meant to call out the Home Guard permanently and as a whole in areas where it applied, but only certain units needed for special tasks.
Naval measures to resist invasion were carried a stage further on 13th September,, when the Nelson and the Hood moved from Scapa Flow to Rosyth.25 The battleship Revenge had already been ordered to Plymouth and moved later (on nth October) to Spithead. The system of air reconnaissance patrols, already modified early in August, was again adjusted to improve the chances of detecting an invasion force hi/the Channel, and ultimately assumed the form shown in Map 19.26 The two Coastal Command groups responsible for most of the patrols--Nos. 16 and 18 Groups--could now call on the equivalent of some nineteen squadrons, as compared with fifteen in the early summer.* Patrols west of 30 W. were flown with aircraft spared with difficulty from long-range convoy-escort by No. 15 Group.
Apart from purely defensive measures something could be done, and in fact was done, to frustrate German preparations or at least to hamper them. As early as the end of June Bomber Command had been ordered to co-operate with Coastal Command in attacking barges; and earlier in the month a naval air squadron had bombed barges at Scheveningen. On 4th July the Air Ministry gave Bomber Command formal directions to pay special attention to enemy ports and shipping in view of the prospect of invasion.27 But this, as we have seen in Chapter VIII, was only one of several tasks assigned to the bomber force. The outcome was that in the whole of July and August
* For details, see Appendix XVIII.
Bomber Command aimed some 66 tons of bombs at barges and shipping outside Germany, 468 tons at aerodromes also outside Germany, and 1,454 tons at German industrial targets and communications. Coastal Command, with its small striking power, aimed some 58 tons at dockyards, shipping, aerodromes and oil-tanks. In terms of the effect of German preparations for invasion, probably the most successful of all the attacks was that made on 12th August on an aqueduct over the Dortmund-Ems canal by five Hampdens, each carrying one bomb. The crews were told to drop their bombs from a low altitude under cover of a high-level diversionary attack by six more Hampdens. Two of the five were shot down as they approached the target, but one crew succeeded in planting their bomb just northeast of the aqueduct in face of intense anti-aircraft fire. For this exploit, which blocked the canal for ten days and thereby delayed the movement of motor-boats to the invasion ports, Flight Lieutenant R. A. B. Learoyd, the captain of the successful aircraft, was awarded the Victoria Cross.
Although pressed home with gallantry, attacks on aerodromes were less effective. In July and August Bomber Command flew 1,097 sorties against aerodromes in the occupied countries and lost 61 aircraft. They destroyed five German aircraft on the ground and damaged twelve.28 Damage to the aerodromes themselves escapes precise assessment, but seems to have caused the enemy no serious embarrassment.
One excellent reason for not sending large numbers of aircraft to attack barges in July and August was the lack of suitable targets. The flow of traffic to the Channel ports in early September removed that objection and gave new urgency to the demand for such attacks. Accordingly, on the nights of the 5th and 6th Bomber Command devoted most of the Blenheim medium bombers to the task.29 Next night twenty-six Hampdens and eleven Battles joined the Blenheims. Afterwards barges and shipping in French and Belgian harbours became the main objective of the whole bomber force, absorbing about three-quarters of the total effort for the month and attracting more than a thousand tons of bombs. On the 13th, when for the first time the whole night's effort was exerted against ports and shipping, ninety-one sorties were flown for the purpose, and on the next night nearly twice that number. On the 17th eighty-four barges were sunk or damaged at Dunkirk and by the 19th the cumulative total had reached upwards of two hundred.30
Partly in consequence of these attacks, which made the nearer Channel ports exceedingly unsafe anchorages for German transports, the Royal Navy found fewer good targets for their guns than might have been expected. On the night of 8th September ships of the 2nd Cruiser Squadron sent to bombard Calais and Boulogne could find
no ships at Calais; and as no barges were seen there either, fire was withheld.31 At Boulogne thick weather allowed only a short bombardment. Next night destroyers of the 21st Flotilla found no ships at Calais and scarcely any at Boulogne. On the 10th, two destroyers and an escort vessel fared better off Ostend, where they opened fire on trawlers as well as barges. Other spoiling operations in September and October included frequent sweeps off the French coast by destroyers and motor torpedo-boats, as well as a bombardment of Cherbourg in the early hours of 11th October by the battleship Revenge, escorted by seven destroyers and six motor gunboats.
Apart from their physical effects, which were substantial but not overwhelming, the air attacks made on invasion ports in September challenged a tendency among some members of the German High Command to assume that the Royal Air Force was on its death-bed.32 The British bomber force was known to have been mulcted of some pilots to replace losses in the fighter force; but the attacks proved that it could still put out a substantial effort on its own account. Fighter Command drove home the lesson on the 15th, when heavy air battles over southern England cost the Luftwaffe sixty aircraft.*33
A week earlier the German Naval Staff had remarked that the undisputed air supremacy needed for invasion was still to seek, but that possibly its attainment was close at hand.34 Discovering within the next few days that, although losses sustained so far could be made good from reserves, the roadsteads off the principal Channel ports could not be used as night anchorages for transports while bombing continued, they had since become less hopeful.35 They were also worried by the failure of the Luftwaffe to take effective action against the British fleet. Remarking that this omission would throw the whole burden of protecting the seaward flanks of the cross-Channel route on to minefields, which could never be a sufficient safeguard, they came to the conclusion that 'SEALION' could not yet be carried out. On 13th September Admiral Raeder told the Führer that Göring's efforts in the air had hitherto failed to 'provide conditions for carrying out the operation'; two days later he was still of the opinion that invasion would be a desperate gamble.
In the next few days bad weather continued to hamper final preparations for the expedition, including minelaying. At the same time forecasts gave no hope of a long spell of fine weather in the near future. Accordingly, the Naval Staff were still in favour of holding
* See Chapter XV.
back when, on the 17th, the time came for the preliminary order for 'SEALION' to be given or withheld. Meanwhile British air opposition showed no sign of decreasing. In these circumstances the Führer decided that 'SEALION' must be postponed.36 He ordered that the possibility of a landing in October should be borne in mind, but that meanwhile the invasion fleet should be partly dispersed in order to prevent further losses. By 21st September more than a tenth of the transports and barges assembled or on their way to their assembly-points had been lost or damaged through British action.* Moreover, as the Führer may have suspected, the disposition of most barges was now known with considerable accuracy in Whitehall from the study of air photographs.37
In effect, these orders disposed of the chance of a landing before the winter. Inevitably a point was soon reached where any further dispersal of the fleet, if thorough enough to give protection against bombing, would prevent the ships from reassembling in time to carry out the plan. Substitution of a new plan involving a longer interval between preliminary and executive orders was mooted but not officially adopted; in any case its execution so late in the year would have been difficult. Hitler was thus forced in October to choose between stoppage of dispersal and indefinite postponement of the whole project. He chose the latter. On the 12th he renounced a landing in 1940, promising the heads of the fighting services that they should have good warning if he later decided to try invasion in the spring or early summer of 1942.38 He ordered them meanwhile to continue preparations calculated to put pressure on the enemy, and to improve the fitness of their commands for the call that might eventually be made upon them. Finally, early in January, 1941, he ruled that all preparations for 'SEALION' should be stopped except the development of special equipment and measures of deception.39
The scattering of the invasion fleet did not go unremarked in London.40 As early as 20th September six destroyers and a torpedo-boat photographed at Cherbourg on the 18th were seen to have left, and arrivals at Brest in the next few days left their destination in little doubt. Similarly there was an obvious dwindling of barges in the invasion ports, the total visible in the five main ports from Flushing to Boulogne declining from 1,004 on 18th September to 691 in the last week of September and 448 in the last week of October. At
* According to German sources the numbers of craft assembled and lost or damaged were:
Assembled Lost or
Transports (including 4 in transit) 170 21 Barges (including 424 in transit) 1,918 214 Tugs (including those in current use) 386 5
In addition, 1,020 motor-boats had left for invasion ports; three of these had been put out of action.
Flushing itself the number quickly fell from 140 to 45, but in late September practically all the missing barges were seen lying in a neighbouring canal. The number at Ostend decreased in the same proportion, and here some barges were actually photographed moving inland along the canal which connects Ostend with Bruges. At Dunkirk the number increased slightly towards the end of the month, only to fall sharply in October, while at Calais and Boulogne the fall was steady.
These facts were plain enough, but their interpretation was no easy task. Dispersal to avoid loss through bombing was an obvious motive, but the deeper implications of the move were hard to fathom, especially as much of the information given by reconnaissance seemed contradictory. Photographs taken in late September and October, while dispersal was in full swing, showed ramps apparently intended for rapid embarkation and disembarkation.41 They also revealed twin barges of mysterious pattern, presumably connected in some way with invasion.42 On the other hand, widespread evidence of constructional work on aerodromes, particularly in Holland but also as far afield as Brittany and Norway, might well mean that the enemy was discarding invasion in favour of an all-out air offensive.43 An added complication was the chance that, under cover of the bustle so plainly evident across the Channel, unseen preparations might be going on in Baltic ports beyond the range of air reconnaissance. A new long-range version of the Spitfire set that doubt at rest on 29th October, when photographs of Stettin, Swinemünde and other ports not previously covered were at last obtained and revealed nothing of great consequence.44
Meanwhile a few barges which put to sea on exercises had been sunk by bombing or bad weather. Some thirty-six bodies of German soldiers were washed up at various points between Yarmouth and Cornwall.45 Hence arose a widespread belief that an invasion fleet had actually sailed and had been badly mauled by our defences. But naturally that belief was not shared by the British Government, the Chiefs of Staff or other authorities whose access to the reports of the Combined Intelligence Committee had enabled them to watch the tide of German preparations flow early in September and mysteriously ebb some three weeks later.
Confusing in many ways as were the signs revealed by air reconnaissance after the third week in September, by the end of the following month--or, as some thought, earlier--they justified the inference that an expedition from the Channel ports was no longer imminent.46 With
Disposition of Home Forces
the coming of autumn the Admiralty withdrew instructions which had restricted the movements of the Home Fleet while the danger seemed acute.47 Soon afterwards they ruled, however, that the Auxiliary Patrol designed to give warning of approaching seaborne forces should be maintained throughout the winter. Thereafter a growing threat to merchant shipping on the Atlantic convoy-routes forced them to disperse a large part of the Home Fleet to distant ports for the greater safety of convoys and to divert to trade-protection more than half the light naval forces hitherto allotted to defence against invasion.*48
Whether, and at what time, the danger might be expected to recur were points not easily determined. If the threat of invasion were revived, light naval forces would again be badly needed, though it was hoped that those available for the purpose would be increased by some or all of the fifty American destroyers whose exchange for certain rights conceded by this country had now been sanctioned by the President of the United States.49 The Chiefs of Staff were confident, however, that if the enemy did decide to try again, his preparations would attract our notice at least some weeks before his fleet could sail.50 They considered, therefore, that the transfer of naval forces from trade-protection back to counter-invasion duties could safely be left until the threat declared itself.51 When the time came the necessary changes could be made in five to seven days.52 To lessen the risk of bombing and of mines laid by German aircraft in East Coast estuaries, counter-invasion forces which then came south would be based on the western half of the Channel, and a cruiser squadron on Rosyth. As the expected warning would not enable the Admiralty to gauge the exact time of invasion, a delay of twelve hours must be expected before the ships could reach the landing-area.
Army plans and dispositions for the winter were governed by broadly similar assumptions. Reviewing the chances of invasion before the spring, the Government concluded at the end of October that a major landing within the next five months could be discounted except in the south-east.53 Their view was that German troops might still be put ashore from self-propelled barges between the North Foreland and Dungeness and that landings from transports might be made in small harbours and on beaches from Orfordness to Poole. Elsewhere only small diversionary expeditions need be feared.
Calculating that two field divisions kept forward in the neighbourhood of Dover and one in Norfolk would suffice to meet this reduced threat, General Brooke proposed to withdraw the rest for training, leaving the defence of beaches elsewhere to troops of lower category.54 By November seven County Divisions, with an establishment of
* See Chapter XVIII.
10,000 of all ranks apiece instead of the 15,500 allotted to the field divisions, and with little artillery or transport, were available for these duties. Plans had been made to build them up to full scale, but lack of manpower threatened postponement.55 Meanwhile withdrawals overseas had reduced the number of full-scale divisions at home to twenty-two, of which six were under orders to go abroad or earmarked for the purpose. In addition, one armoured division remained in the United Kingdom and three more were being formed. To ensure an adequate number of trained troops at home after the winter, the Government and the Chiefs of Staff therefore fixed the rate of overseas reinforcement for the period from January to June at one division a month, with the proviso that the strength at home must not be allowed to fall below twelve divisions in reserve, apart from troops on the beaches.56
These arrangements at last gave Brooke a chance of putting the Field Force through a much-needed course of training in mobile warfare. The bulk of the troops spent the winter learning to go into action immediately after completing forced moves of up to two hundred miles in mechanised transport or forty miles on foot. Routes appropriate to every imaginable contingency were reconnoitred; comprehensive schemes for the control of military traffic and the movement of refugees were drawn up; and rehearsals for the hypothetical battles of 1941 included practice in rounding up parachutists who might be landed to block communications. On completing their training the divisions took up the positions shown in Map 20.
The winter also gave time for a further overhaul of arrangements for higher command and for co-operation between formations of different services. Eastern Command, which covered practically the whole of the probable invasion area from the Wash to the Channel coast, had too wide a commitment. Accordingly a new South-Eastern Command was formed to take care of the area south of the Thames and as far west as Western Command's new boundary just east of Portsmouth.57 Exercises designed to test plans for an all-out effort by the metropolitan air force against an invader provided some lessons whose interpretation gave the Air Staff much to think about. The defended ports were re-classified, the old categories appropriate to peacetime preparations giving place to a new division into 'major' and 'minor' ports.* In December, Coastal Command adopted a contingent plan of anti-invasion reconnaissance, to which effect would be given only when the danger reappeared; meanwhile anti-shipping and general reconnaissance patrols were continued in accordance with a scheme set out in Map 21. Finally, to ease the task of defending shipping in the North-West Approaches, in April the
* For details, see Appendix XIX.
Coastal Command Scheme of Anti-Shipping & General Reconnaissance Patrols
20th December 1940
Admiralty assumed operational control of Coastal Command.58 The command remained under the Air Ministry for administration and training, its functions being substantially unchanged. Effect was thus given to an agreement between the Admiralty and the Air Ministry which had been reached in principle in the previous December.
On the approach of spring the Chiefs of Staff completed an exhaustive review of the possibilities of invasion in the coming season and of the resources available to meet the threat. They reasoned that the enemy would be eager to end the war in 1941, but would probably try all other means of doing so before he ventured on a gambler's throw.59 Nevertheless, they believed that full provision to resist a landing was indispensable. They estimated the strength of the German forces which might be used at six armoured, four airborne and twenty-six infantry divisions, supported by more than two thousand bombers and dive-bombers, fifteen hundred fighters and a thousand transport aircraft. They thought, however, that as many as fourteen thousand aircraft might conceivably be mustered if the enemy decided to stake all his capital on a colossal gamble.60
The first part of this estimate was reasonable enough, but the second flattered the Luftwaffe considerably. Towards the end of March the German air force had on all fronts some nineteen hundred bombers and dive-bombers and seventeen hundred fighters, or with other categories a total of about five thousand machines, including transport aircraft. About two-thirds of these machines were serviceable.61 In the circumstances postulated by the Chiefs of Staff the total might have been substantially increased by squandering reserves and training units, but could scarcely have been raised to more than half the British estimate by even the most unbridled gambler.62 As for the air forces on the front immediately facing the United Kingdom, when the estimate was made removals to the Balkans and Sicily, with wastage incurred in recent night flying from wet aerodromes, had already weakened them considerably, and further transfers to distant theatres were in view.63 In the light of current knowledge the Chiefs of Staff were bound, however, to assume that units moved away from the Western Front might come back later in the year.
Meanwhile, as the Führer had predicted, the British Army was much better trained and equipped to resist invasion than in 1940, though the Chiefs of Staff would still have liked more armour. Hence they recommended that for the time being no armoured units should leave the country.64 ln general, the Chiefs of Staff endorsed the measures already taken or contemplated by the fighting services. The bomber force, now some seven hundred aircraft strong and in process of re-equipment with heavier and faster bombers, seemed to them likely to do great damage to shipping which might reassemble in the nearer invasion harbours, and signs of readiness across the Channel
would, they thought, give reasonable time for the diversion of destroyers from trade-protection. Fearing a landing in Eire, which the navy and the air force might not be able to prevent, they recommended a strengthening of land forces in Northern Ireland; in other respects they could suggest no alteration of Brooke's dispositions, although their old fear that a force rushed across the Straits of Dover might escape our naval forces was still present. Finally, they summed up their opinion of the outlook by pointing out that, while invasion seemed to have grown less likely, 'the Germans, with their aerodromes already established in north-west Europe and with a highly-developed system of roads and railways, could always concentrate for invasion far more quickly than troops despatched overseas could be brought back to this country to meet the threat.65 They concluded that, while their policy must be to avoid playing into the enemy's hands by keeping inordinately large forces mewed up in the United Kingdom, they must also avoid important overseas commitments other than those already existing in the Balkans and the Middle East. For in Europe a fresh phase in the struggle for control of the Balkans had just been opened by the decision of a new Yugoslav Government to resist the Axis powers; and in North Africa a critical stage had been reached with the arrival of German armoured formations and air forces to strengthen the discomfited Italians.
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