ACCORDING to the Chiefs of Staff, the return of the British Expeditionary Force to the United Kingdom 'revolutionised the home defence position.'1. This was true, however, only in the sense that henceforth equipment, not manpower, was the ruling factor. More than 224,000 officers and men came back from Dunkirk and its neighbourhood towards the end of May and in early June, and ultimately another 144,000 from ports further west.2 But the returning army left behind it practically the whole of its heavy equipment, including some six hundred tanks, more than a thousand field guns or guns of larger calibre (to say nothing of about five hundred anti-aircraft guns), some 850 anti-tank guns, many thousands of anti-tank rifles and large numbers of lorries, cars and motorcycles, besides huge quantities of ammunition and supplies.3 Nominally twelve divisions were at one stroke added to Home Forces. But the augmented force would not become an effective weapon until a great part of these losses, with the deficiencies of the original home defence divisions, had somehow been made good.
The magnitude of the task is shown by one example. Deliveries of 25-pounder field guns had risen slowly from less than one a month in the first quarter of 1939 to roughly thirty-five a month at the time of the withdrawal. The establishment of a single home defence division was more than seventy; and there were now twenty-seven such divisions, whose equipment must be provided or replenished largely from new production. Similar considerations applied to many other weapons, including the anti-tank guns which would be so sorely needed if the enemy came ashore with armoured fighting vehicles. A number of substitutes for anti-tank guns were suggested, including mortars of new design which ultimately proved very valuable; but these, too, had to be manufactured and distributed before they could be used.
The narrow escape of the flower of the British Army, illumined by the memorable and moving words in which the deliverance was
announced by the Prime Minister, roused the inhabitants of these islands to an awareness of their country's danger, and a determination to avert it by all means in their power, for which no parallel can be found at least since Napoleonic times, and perhaps not since the crisis of 1588. After the German successes in Poland, Denmark, Norway, Holland, Belgium and now France, avoidance of the fate which threatened to overwhelm the United Kingdom in its turn might well seem unlikely; but if it occurred to observers in this country to entertain such thoughts, few who listened to Mr. Churchill's speeches can have doubted that any sacrifice they themselves might offer was infinitely preferable to acquiescence in defeat. Henceforward Government and people shared in a mighty effort to ensure that whatever perils the next few months might bring to their homeland should not find its defenders unworthy of their heritage.
Among immediate tasks, the most far-reaching in its effect on the national life was a vast acceleration of the output of almost every kind of war material. It was tackled resolutely, and on the whole with remarkable success. From that fact has sprung the legend that early in June the British people, awaking suddenly to their nakedness, proceeded to clothe themselves with lightning speed. The true course of the production drive, if no less creditable to those concerned, was less spectacular. In most respects the summer's effort was not so much a sudden spurt as a steady uphill slog. A big increase in deliveries of fighters from May onwards--achieved to some extent by mortgaging the future to the present--has already been recorded.* These excellent results owed much to the driving spirit of Lord Beaverbrook, something to plans laid earlier and now beginning to bear fruit, and perhaps most to a new determination among all employed in the factories concerned to do more than had hitherto seemed possible. The output of certain types of bomber, too, was raised at the expense of others less urgently demanded. But such expedients could not, in the nature of things, be applied throughout the field of war production. Deliveries of infantry and cruiser tanks showed a gradual upward trend in June, July and August, averaging 123 a month for the three months; on the other hand, output of wheeled vehicles remained almost stationary at roughly 9,000 a month. Monthly deliveries of field guns reached and remained at 42 in May and June, but rose thereafter to 60 in July and 72 in August. The total was still far short of the number potentially required. Nor was American industry yet in a position to do much, although the arrival later in the year of roughly half a million rifles went some way to solve the problem of equipping the Home Guard.
* See p. 121.
GHQ Line Covering the Principal Production Centres
Largely because of this lag in production, but also on account of other factors which delayed the absorption even of existing stocks, Home Forces continued throughout the summer to be dogged by shortages of almost everything they needed to oppose an invader expected to achieve high standards of speed and hitting power. Big additions to his manpower did, however, enable General Ironside to reconsider his problems and evolve a new plan of defence. As he now saw it, his first aim must be to 'prevent the enemy from running riot and tearing the guts out of the country as had happened in France and Belgium.4 He concluded that, at all costs, his troops must be deployed in sufficient depth to ensure that any substantial German force that got ashore could be halted before it reached London or the industrial Midlands. At the same time they must be ready to intercept any reinforcements whose arrival the navy and air force were unable to prevent.5
To achieve both aims in the circumstances existing in the summer would be very difficult. For the most part the troops at the Commander-in-Chief's disposal were not only ill-equipped; they also lacked mobility, and their training had not envisaged tasks of the wholeheartedly offensive character which German tactics now seemed likely to impose. There were nearly five hundred miles of beach on the South and East Coasts suitable for the landing of armoured fighting vehicles, and about a third of this expanse of coast was in the neighbourhood. where the invader could be most strongly supported by air power.6 At the same time, airborne troops might land a long way from the sea. In the absence of strong mobile forces deeply imbued with the offensive spirit, Ironside came to the conclusion that his best chance lay in combining his few mobile columns with static defences deployed over a wide area.7 The pivot of the new plan which he and his staff worked out in June was a G.H.Q. line of anti-tank obstacles covering London and the Midlands, supplemented by a series of command, corps and divisional stop-lines sited further forward. (See Map 7.) The G.H.Q,. line, following natural obstacles such as waterways and steep inclines where they came to hand, ran from the neighbourhood of Richmond in Yorkshire to the Wash, and thence through Cambridge to the Thames at Canvey Island; south of the Thames it continued through Maidstone and Basingstoke to Bristol. Of the forward stop-lines, five ran across the Eastern Counties to check an advance from the vulnerable beaches about Lowestoft, either towards the Midlands or across the open uplands north of London. Three crossed Surrey, Kent and Sussex, barring the approaches to the capital from that direction. Generally the role of divisions in front of the G.H.Q. line was to exploit the forward stop-lines so as to confine, break up and delay an advance from the coast, thus giving time for the arrival of mobile
forces from the G.H.Q,. Reserve. Accordingly, most 0f the 786 field guns available in the middle of June were sited near the coast to cover the most likely landing places, while conversely the better part of the 167 anti-tank guns which Ironside could muster were kept back in G.H.Q,. Reserve. To gain further time, beaches were mined and obstructed, roads leading inland were blocked, and stocks of incendiary grenades and 'sticky bombs' (for dealing at close quarters with armoured fighting vehicles) were provided at every guard-post. Auxiliary units were trained to work in the rear of an invader, harrying his advancing columns and cutting them off from supplies of water, food and petrol.
Manifestly these tactics, harassing rather than destructive as they clearly were, would be effective in the long run only if the mobile forces, when they did arrive, could deliver something like a killing punch. And here, unfortunately, Ironside was very weak. In the middle of June his general reserve included three of the better-equipped infantry divisions and the 1st Armoured Division. The last, having left behind in France 100 infantry, 163 cruiser and 354 light tanks, had returned to the United Kingdom with nine tanks all told; and its effective strength at the end of June consisted of 81 medium tanks which had reached it in recent weeks as an instalment of its new equipment.8 In addition the 2nd Armoured Division, now with 178 light tanks, had moved to a position between Northampton and Newmarket, whence it could strike, as best it might with limited resources, at the rear and flank of an invader pressing inland either from the East Anglian coast or from points north of the Wash. The infantry divisions remained in the area Northampton-North London-Aldershot, in order that they might advance as rapidly as possible by brigade groups to any threatened area. The number of tanks in the United Kingdom was, indeed, much greater than the total of the effective strengths returned by the two armoured divisions; but the fact remains that most of them were not considered fit or available for use by the only formations that could use them.*
Among the more obvious weaknesses attending these arrangements were an insufficiency of anti-tank guns to support both the forward lines and the G.H.Q. line; a lack of local reserves, as distinct from the G.H.Q. Reserve; and a lamentable shortage of the armour needed to give counter-attacks by the mobile forces a good chance of success. The plan was designed to make the best of a bad job where the first two were concerned, by allotting preference to the main line of defence; but the third was radical and inescapable. With four armoured divisions in reserve the Commander-in-Chief would have felt that the country was reasonably secure; as it was he had, in his
* Compare p. 124.
own words, 'less than half the equivalent of one complete division'.9 For air support he could call in the first instance on two medium-bomber squadrons held at his direct disposal, and on five reconnaissance squadrons, of which two were allotted to Eastern Command and one each to Northern, Western and Scottish Commands.10 The nature and extent of any further assistance from the air force would clearly depend, in practice if not in theory, on the scope and outcome of the air battles which must be expected to precede or accompany invasion.
Should the invader come, or should his coming seem imminent, the plan would be put into effect by issue of the code-word 'Cromwell'. On receiving it troops would go at once to their battle-stations; and essential telegraph lines would thereupon be taken over by the army.
In the meantime some progress had been made with the special measures of coast defence begun in May. By 12th June a first batch of 46 new batteries, each comprising two 6-inch naval guns and two searchlights, had been added to the fixed defences and was ready for action.11 As the army was short not only of guns but also of coast defence troops, half these guns were manned by marines or naval personnel until army crews became available later in the summer. Their primary role was seaward defence. In order to save ammunition, conceal the positions of the batteries as long as possible and offset inexperience, the gunners were told to hold their fire until the enemy began to lose sea room some three to four miles from the shore; the guns would thus be limited to about half their effective maximum range of 12,000 yards. Beach defence was a secondary role. The guns and lights were carefully hidden with nets and bunting, later supplemented by disruptive painting.12
Even with these additions the fixed defences left many places unguarded or inadequately protected. At Dover, for example, the arrival of the Germans on the opposite side of the Straits raised some awkward issues. The Dover mine-barrage became largely ineffective, since German ships could now avoid it by hugging the French coast.13 Furthermore, the enemy not only commanded his own side of the Channel, but by mounting long-range guns near Calais and by basing aircraft in the neighbourhood was able to dispute command of the Straits themselves.14 Besides four 6-inch guns with a range of 12,000 yards, the fixed defences at Dover included two 9.2-inch guns, whose extreme range was about ten miles.15 Two modern 6-inch batteries, whose guns could fire to 25,000 yards, were being installed as rapidly as possible, and four g-2-inch guns on improved mountings promised to increase the range of the defences to 31,600 yards (later increased by supercharging to 36,300 yards, or roughly twenty miles). But the new guns were not yet ready. Meanwhile the enemy
had the power to come at least half-way across the Straits without interference from shore-batteries, while his own artillery and aircraft gave potential protection against British naval craft and bombers. Waters whose narrowness was in any case ill-suited to major naval operations were thus made doubly dangerous to our larger warships, and even patrols by lighter craft seemed inadvisable in daylight while the shortage of destroyers was acute. The destroyers hitherto at Dover were withdrawn to Portsmouth.16 Our command of the Straits was thus much weakened, though the shipping-lanes were still swept and local convoys continued to pass through them, making the best use of darkness.
As a possible remedy Vice-Admiral Ramsay suggested that a number of long-range guns should be installed at Dover and put at his disposal, contrary to the usual practice which allotted immediate control of coast-defence guns to the army.17 A naval 14-inch supercharged gun, with a theoretical range of more than twenty-seven miles, was in fact available; but it proved unsuitable for engaging moving targets, and in practice was seldom used for fear that the enemy's more effective weapons might reply.18 No more guns with sufficient range to fire across the Straits could be emplaced before the end of 1940. Meanwhile the enemy enjoyed a considerable advantage. The chance that a sudden descent on the coast of Kent in fog or darkness might enable him to pass a stream of traffic across the Channel continued, throughout the summer, to trouble strategists not convinced of his reluctance to try invasion without first winning a major battle in the air.19
In general the chief danger was that the weakness of the fixed defences might give the Germans an opportunity of landing armoured and other vehicles and artillery. Infantry without field guns or transport would be relatively harmless. The measures taken since May to deny ports to the enemy were intended to reduce the risk by depriving him of the quays and cranes which he would need to unload such gear from ordinary transports.20 Apart from demolition schemes for more than a hundred ports and harbours in all parts of the kingdom--for ultimately the plan was extended right round the coast--blockships were provided at some fifty places.21 There remained the risk that in fine weather armoured fighting vehicles carried in special craft might come ashore on beaches. To prevent such craft from entering the Thames, the Humber and Plymouth harbour, anti-boat booms similar to those provided at Dover, Harwich and Rosyth were installed there in the early summer.22 To hinder access to open beaches, about a hundred miles of a fighter and simpler form of boom, consisting of horizontal wire nets supported by floating canvas tubes filled with kapok, were laid by five specially-commissioned vessels assisted by local craft. In addition, about eighty
Coastal Command Anti-Invasion Patrols
16th July 1940
miles of an alternative obstruction, in the form of mines attached to wire jack-stays, were installed. The Wash was guarded by a defensive minefield and a light boom some five miles long. As floating defences were difficult to lay and maintain in unsheltered waters, a more durable substitute was later adopted, in the shape of a line of builders' scaffolding erected below high-water mark and armed with mines. Some seventy miles of coast were thus protected.23 About three hundred miles of scaffolding, besides buried mines, were used above high-water mark as beach obstructions. Elsewhere a variety of obstacles was installed to hold up troops who tried to wade ashore and to prevent the landing of troop-carrying or other aircraft on drying mud-flats.
A number of less orthodox measures owed their genesis to Lord Hankey, whose long career at the Committee of Imperial Defence and elsewhere had led him to a seat in Mr. Chamberlain's War Cabinet and to the Chancellorship of the Duchy of Lancaster in Mr. Churchill's Coalition Government.24 As early as 1914 Captain Hankey, as he then was, had been stimulated by the account in Gibbon's Decline and Fall of the Roman Empire of the 'Greek fire' used by the Byzantine emperors, to an active interest in the lethal possibilities of petroleum. Flame-throwers which used petroleum had been employed by both the Central and the Allied powers between 1915 and 1918, but interest in them had lapsed in this country. In 1940 the dearth of conventional anti-tank weapons after the withdrawal from Dunkirk, and the general sense of urgency, created an atmosphere exceptionally favourable to new suggestions. Conceiving the idea of 'burning the invader back into the sea' with fuel which would otherwise be wasted, Lord Hankey found a ready collaborator in Mr. Geoffrey Lloyd, whose position as Secretary for Petroleum enabled him to draw on the resources of the oil industry. Mr. Churchill and the Chiefs of Staff approved their suggestion that experiments should be carried out and that the results should be made available to the various Home Commands.
Early in June a small Petroleum Warfare Department was created, with Mr. Lloyd as Minister in charge. Its Director-General was Sir Donald Banks, a senior civil servant with considerable experience as a soldier. Under the general guidance of Lord Hankey and Mr. Lloyd, and with the willing help of the leading oil companies, short stretches of road leading inland from likely landing-places were lined with perforated pipes, connected in each case with a fuel-tank hidden at a higher level. On the enemy's approach a member of the Home Guard waiting in an adjacent observation-post would flood the road with petrol and ignite it by throwing in a flaming missile. Later, remote control and automatic ignition were introduced. Similar arrangements were made in some cases on the beaches
themselves; and at a few places--notably on the long hill between Dover and Canterbury--a small power-pump made it possible to cover a hundred yards or more of road. In addition to these 'Static Flame Traps', a number of 'Flame Fougasses', each comprising a group of forty-gallon drums containing various highly-inflammable materials, were installed in lieu of minefields at points where vehicles might be expected to slow down. Other devices tried but less generally adopted included petrol-containers disguised as wayside tar-barrels, or so disposed that they could be lobbed or cast from a height on to the invader; and anti-tank ditches filled with liquid petrol or with petrol-soaked peat.
Attempts to 'set the sea on fire' by means of pipes intended to cover the surface with burning petrol promised well at first, but then met many difficulties. Originally the pipes were made to terminate below high-water mark, where heavy seas often interfered with their working and sometimes even threw them back on to the beach. After a series of experiments extending well into 1941 their termination above high-water mark was found to provide a much more reliable and formidable weapon. Experiments by the Petroleum Warfare Department and other authorities with improved flame-throwers of various kinds had a long and difficult gestation, but gave birth at last to devices of great value, used in many theatres. In the meantime steps were taken, by means of open propaganda and calculated indiscretions, to give the enemy a not-unfounded impression that, if he tried to land, he would be greeted by an awe-inspiring array of novel and unpleasant weapons.
So much for the arrangements made to impede the enemy when he had landed or as he prepared to come ashore. He could, however, also be attacked at his points of departure and on passage. The first method, whose advantages had long been recognised and were summed up in Nelson's famous dictum, 'the enemy's ports are our first line of defence', was one in which the bomber force could hope to play a useful part. Theoretically, aircraft were also well suited to attack on passage, but in practice a strong force of bombers and torpedo-bombers adequately trained for such a role was lacking. In any case, the primary responsibility for repelling a would-be invader before he landed rested with the navy.
The chances of catching an invasion fleet before it sailed or on passage would depend to a great extent on the warning provided by air reconnaissance and other sources of intelligence. In the light of
experience gained since the beginning of the war, the Admiralty judged that adequate warning could not be relied on?.25 They concluded that their best course was to be prepared to deal with the enemy as he arrived, without committing themselves to dispositions likely to debar them from seizing opportunities of earlier engagement.
At the beginning of June the Home Fleet was weaker than at any time since the previous winter. (See Appendix IV.) Of the eight capital ships in home waters, only four--the Rodney, Valiant, Renown and Repulse--were immediately available for North Sea operations.26 The Nelson and the Barham were refitting, the Hood was undergoing repairs and was about to join a foreign station, and the Resolution was on the point of leaving the Home Fleet for the Western Approaches Command, whose duties were mainly concerned with the defence of ocean trade. The Norwegian campaign and the withdrawal from Dunkirk were both in progress and were making heavy demands on the Home Fleet's cruisers and destroyers.
A month later the position was only slightly better.27 (See Appendix V.) The Nelson and the Barham had returned or were about to return to duty; but the aircraft-carrier Glorious had been sunk while on her way from Norway, and fear that the French Mediterranean fleet might fall into German hands had taken a strong force to Gibraltar. The Hood, the Valiant and the Resolution, with the aircraft-carrier Ark Royal, the cruisers Arethusa and Enterprise and thirteen destroyers were all based on that station. The ships at home or in adjacent waters comprised the five capital ships Nelson, Rodney, Renown, Repulse and Barham, the aircraft-carrier Argus, eleven cruisers and eighty destroyers. Of these, the capital ships (with the temporary exception of the Barham, still at Liverpool), all but one of the cruisers and fifty-seven of the destroyers were at bases more or less commanding the approaches to the East Coast. But local striking forces in the neighbourhood where a landing seemed most likely were very weak. The Nore Command had only nineteen destroyers at the Humber, Harwich and Sheerness; and the Chiefs of Staff considered nearly twice that number necessary for safety.28 Dover (formerly a sub-command but now directly under the Admiralty) and Portsmouth had five destroyers each. Apart from the heavy ships and cruiser and flotilla forces, twenty-five fast minesweepers and 140 minesweeping trawlers were responsible for maintaining searched channels between Sunderland and Portsmouth, and an Auxiliary Patrol of up to 400 trawlers and small craft was disposed all round the coast from Invergordon to Portland to give warning of approaching hostile forces and attack them.29 Besides a fluctuating proportion of the thirty-four sloops and corvettes normally used for escort duties, other vessels available for defence against invasion included about
a hundred Harbour Defence Patrol Craft, of which roughly half were on the East and South Coasts, and a few Armed Examination Vessels and gunboats in the Forth and Thames.30 Altogether about seven hundred armed patrol vessels of one sort or another were available for off-shore reconnaissance; and throughout the summer some two to three hundred of them were constantly at sea in the threatened area between the Wash and Sussex.31 For reconnaissance at greater ranges the Admiralty relied on submarines--of which there were thirty-five--and aircraft.
How these forces, or others which might replace them, could best be used to repel invasion was not easily decided. The outline of the Admiralty's first plan was drawn at the end of May, to the accompaniment of fast-moving events which included the withdrawal from Dunkirk and the closing stages of the campaign in Norway. At that time the future was more than ordinarily obscure; and even later much doubt existed as to when invasion would come and the form that it might take. To support a direct assault by sea, the Germans could count on mustering at most two battle-cruisers, two old battleships and five or six cruisers, with perhaps some ten destroyers.32 Their possible courses of action included a diversion to the north, perhaps in the form of an attack on our Northern Patrol by their battle-cruisers, and a southward dash towards the East Coast from German and Norwegian bases. In the latter all their cruisers and possibly their two old battleships might take a hand.33 Whether the enemy would risk his battle-cruisers in the southern part of the North Sea was doubtful; but an attempt by his less-valuable ships to force the Straits of Dover was not unlikely. If he took the Channel ports--as he soon did--the prospect of a landing on the South Coast would be correspondingly increased. Another possibility was a subsidiary or diversionary attack on Ireland.
The Admiralty considered that to counter all these possible moves by the enemy's main fleet they must have ready at least five heavy ships and one aircraft-carrier, with a minimum of two flotillas of destroyers.34 The threat of a northward diversion and a simultaneous move towards the East Coast they proposed to meet by organising the Home Fleet in two divisions, each of which (with the Nelson but not yet the Barham back in service) could be made strong enough to cope with any situation likely to arise in the North Sea. They therefore suggested to Admiral Forbes that his best-protected ships, the Nelson and the Rodney, should move south to Rosyth, and that they should be joined there by as many six-inch cruisers of the Southampton class as the Nore Command could spare.35 They contemplated moving the Valiant and the Repulse to Plymouth, leaving the Hood (whose orders to proceed elsewhere were temporarily in abeyance) with the Renown at Scapa Flow. The aircraft-carrier Ark Royal, whose long endurance
specially fitted her for the task, should, they suggested, remain constantly at sea to westward of a line from Iceland to the south of Ireland, accompanied by one eight-inch cruiser.36 All available eight-inch cruisers (which were vulnerable to air attack and would therefore be safest on the West Coast) would accordingly be stationed in the Clyde. The lighter six-inch cruisers of the Arethusa class, with such sloops, corvettes and anti-aircraft cruisers as could be spared from escort duties, would be spread round the coast to support a striking force of thirty-six destroyers, organised in four flotillas based on the Humber, Harwich, Sheerness and Dover (or alternatively Portsmouth).37 Even without the Barham there would thus be enough heavy ships at Rosyth and Scapa Flow to deal with a threat to the East Coast. If, on the other hand, a landing on the South Coast were attempted, the destroyers at Dover or Portsmouth, assisted by submarines, could be supported by the Valiant and the Repulse from Plymouth. Between them the Ark Royal and the ships at Plymouth should be able to take care of Ireland.
Within the next few weeks the departure of the Hood, the Valiant and the Ark Royal to Gibraltar--though partly offset by the return of the Barham--precluded their taking up the positions thus tentatively assigned to them, and left the Home Fleet with five capital ships instead of the six needed to put two each at Scapa Flow, Rosyth and Plymouth. A still greater obstacle to the plan was that the Commander-in-Chief, Home Fleet, who would have to put it into practice--and whose opinion was therefore of great weight--disapproved of it. Admitting that events might ultimately compel him to send some at least of his capital ships to Rosyth, Admiral Forbes preferred to keep them at Scapa Flow until he was sure that a German expedition was assembling.38 In the meantime he believed that, although the Germans might possibly land in Ireland, they were most unlikely to attempt a landing in England while our air forces were intact and undefeated.39 The Admiralty responded by telling him that readiness to counter an invasion across the North Sea must nevertheless remain his^major responsibility until he received instructions to the contrary.40 But his preference for Scapa was not challenged, especially as the only German battle-cruiser in good shape towards the end of June--the Gneisenau--was known to be at Trondheim.41 Her sister-ship, the Scharnhorst, had returned to Kiel, but had been damaged by naval action and was wrongly thought to have been hit by bombs. For the moment, therefore, the circumstances which might call for the move to Rosyth seemed unlikely to arise. After further discussion the Admiralty ruled in July and August that the heavy ships of the Home Fleet should go south to break up a landing on the East Coast only if the presence of German heavy ships in the southern part of the North Sea was reported.42
Accordingly the capital ships remained throughout July and August at Scapa Flow, or cruising within prudent limits.43 Cruisers were distributed among the home commands, and destroyers disposed as circumstances--rather than the plan drawn up in May--dictated.44 The bulk of the destroyers were at sea every night, and by day were ready to reach any threatened point within two or three hours of receiving an alarm. By the end of July the Nore Command had thirty-two destroyers (and five corvettes) instead of the nineteen available at the beginning of the month.
In view of these arrangements, and assuming that the destroyers would be strongly supported in an emergency by fighters, the Naval Staff believed by the middle of the month that surprise crossings by small craft, which had seemed so alarming a possibility a few weeks earlier, could now be reckoned 'a most hazardous undertaking' for the enemy.45 They admitted, however, that the venture was still possible. On 10th July they estimated that, in favourable conditions, 12,000 troops might be landed by such means between the Wash and Dover, and perhaps 5,000 between Dover and Land's End.46 A larger force would, they thought, have great difficulty in reaching the South Coast without detection. Should a more ambitious expedition, involving perhaps fifty ships of moderate size, be made from German harbours in thick weather, they believed that possibly 50,000 men with armoured fighting vehicles might get ashore on carefully chosen beaches between Rosyth and Southwold.
We have seen in the last few paragraphs that, while in some respects British plans to meet invasion in the summer of 1940 were based on the assumption that the blow might fall at any moment, they were modified in others by the reflection that the Germans were unlikely to attempt a landing without first joining battle in the air. Without going so far as Lord Keith--who declared on a famous occasion in the nineteenth century, T do not say the enemy cannot come: I only say he cannot come by sea'--Admiral Forbes expressed the more hopeful view when he wrote: 'The enemy has realised that he can only defeat this country if he can sever our lines of sea communication. He knows that he cannot do it by surface forces, and hopes to do it by air and submarine forces.'47
The Air Staff were substantially of the same mind as Admiral Forbes. In their view, seaborne invasion was 'not a practicable operation of war' unless Fighter Command were first defeated.48 If Germany did mean to invade this country, she must begin by gaining air superiority over the approaches to it.
This attitude could be regarded as a logical extension of the opinion expressed by the Chiefs of Staff in their 'stocktaking' review in May; but whether it implied that invasion was not a present danger depended, of course, on the account which the fighter force could be expected to give of itself in such a contest. On the whole, the outlook in this respect was considerably more favourable in July than it had appeared two months earlier. The fighting in France had cost the air force the best part of a thousand aircraft, including nearly five hundred fighters;49 but before the month was out the fighters lost had been replaced, although the relatively experienced pilots shot down over France were a different matter.
It followed that henceforth the main preoccupation of the fighter force must be readiness for the air assault which--according to the Air Staff--would precede any attempt to land substantial German forces in this country. The bomber force would make its contribution by striking at German air bases, aircraft factories and ancillary plants, and in case of need at ports where an expedition might assemble or was known to be assembling.
Meanwhile, Coastal Command had a vital part to play. Apart from its responsibility for spotting an invasion fleet on passage, it now had the task of detecting preparations which might well begin before the preliminary air battle had been fought. In general, photographic reconnaissance was unquestionably the best means of detection, although unfortunately some possible places of assembly were too far away to be photographed by aircraft yet in service. As it was desirable that one commander should be responsible for detecting both preliminary moves and a fleet on passage, Air Marshal Bowhill took control of the Photographic Development Unit--renamed the Photographic Reconnaissance Unit--which was now the main source of air photographs submitted for examination to the Photographic Interpretation Unit at Wembley. The unit at Wembley also dealt with the relatively few photographs taken by the general reconnaissance squadrons, while Bomber Command--which had its own Interpretation Unit--sent to Wembley those of the photographs taken by its squadrons which were not of purely domestic interest. A special Combined Intelligence Committee--comprising in the first instance two naval officers and one each from the army and the air force--had already been set up in London to examine and collate all evidence bearing on invasion, whether from photographs or otherwise.50 To meet the risk that an expedition might sail without warning, the general reconnaissance squadrons daily flew an elaborate series of patrols--including occasional sorties by aircraft fitted with the new A.S.V. (Air-to-Surface-Vessel) radar--Resigned to cover all probable approaches to the United Kingdom.51 Map 8 shows the programme for a typical day in the middle of the summer.
The tasks to be performed by the air force if and when invasion was once launched were laid down by the Air Staff only in broad terms.52 Their plan recognised three 'principal phases' of invasion. First would come the assembly of troops and shipping at the points of departure; next the voyage from the Continent to the British Isles; finally the establishment of a bridgehead. Bomber Command's task would be to attack, in the first phase, the enemy's embarkation ports and ships assembling there; in the second phase and the early part of the third phase, ships on passage. Later in the third phase, the bomber force would switch to German troops and their equipment on British soil. Coastal Command would continue its reconnaissance programme throughout all phases, would take every opportunity of attacking German ships, and during the second phase would also provide long-range fighters to protect our naval forces if they engaged the enemy on passage. The task of Fighter Command, again in all three phases, would be to oppose the enemy's air forces, and above all to beat off attacks by his dive-bombers during the second and third phases. If, however, the Air Staff were right in thinking that invasion would not come unless our fighter force were first defeated, the chances of carrying out the later stages of this programme would be small.
Throughout the summer months that part of the Air Staff's plan which aimed at the detection of an invasion force before it sailed or on passage was carried out to the furthest extent permitted by the weather and the means available. Between mid-June and the end of August over 300 sorties, of which a high proportion covered possible invasion bases for the benefit of the Combined Intelligence Committee, were made by aircraft of the Photographic Reconnaissance Unit from bases at Heston (near London), St. Eval (in Cornwall), Wick (in the north of Scotland) and Leuchars (on the Firth of Forth).53 Some of this work was done by Hudsons; the greater part by Spitfires specially lightened to increase their speed, range and ceiling. Thousands of photographs were minutely scanned, and the scraps of evidence they furnished compared with information from other sources. Aircraft of the general-reconnaissance squadrons set out at dawn and towards evening to quarter the North Sea from the Shetlands to East Anglia; the approaches to the British Isles from east, south and south-west were searched at least once daily unless the weather was prohibitive, and at night continuous patrols were flown between the Humber and the Nore to detect fast light surface craft if they should leave Dutch ports after sunset. The Channel ports from Dunkirk to Dieppe and from Le Havre to Cherbourg were watched at frequent intervals--normally twice daily--and in moonlight or at close of day an aircraft reconnoitred Brest.
Thanks largely to photographs brought back by the Photographic
Plate 7. Hudson Aircraft of Coastal Command on Patrol over the North Sea.
Plate 8. Destroyers on Patrol off the East Coast.
Plate 9. General Sir Edmund Ironside, General Officer Commanding-in-Chief, Home Forces, May-July, 1940.
Plate 10. General Sir Alan Brooke, General Officer Commanding-in-Chief, Home Forces, July, 1940-December, 1941.
Reconnaissance Unit and to the expert work of the interpreters at Wembley, an invaluable picture of German preparations for invasion was built up. With their first report at the end of May the Combined Intelligence Committee were able to scotch alarmist rumours by pointing out that there was 'nothing at present to indicate any large movement of troops or aircraft intended for the invasion of the United Kingdom, and insufficient evidence to suggest when , invasion will start, where forces will assemble or their objective'.54 About ten days later reports from Stockholm, which mentioned substantial movements of German troops to Norway, were outwardly corroborated by signs of naval activity at Trondheim; and towards the end of June unusually large numbers of barges were seen in Dutch waters. But in general the photographs examined up to the end of August gave little support to the view that German preparations to invade this country were well advanced.55
Meanwhile Bomber Command, under Air Marshal Sir Charles Portal, devoted some of its attention to the enemy's air bases and aircraft industry. The Air Staff decided on 19th June that for the time being the primary aim of the bomber force must be reduction of the potential scale of air attack on the United Kingdom,56 but the directives which they framed in consequence proved too wide to achieve their purpose. On the 20th they ordered that both heavy and medium bombers should attack first aircraft factories, secondly communications, thirdly oil targets and fourthly crops and forests. One squadron of Hampdens, already occupied in laying mines in enemy coastal waters, would go on doing so. In addition, the medium bombers were to seize opportunities of bombing aerodromes in France and the Low Countries. Less than a fortnight later reports of impending invasion, arising chiefly from the abundance of barges in Dutch waters, caused the emphasis to shift momentarily to ports and shipping. Soon afterwards the Air Staff not unnaturally came to the conclusion that too many targets were being tackled.57 They therefore ordered that for a limited period the heavy squadrons should concentrate on ten aircraft factories and, less urgently, on five oil plants, while the mediums devoted their main effort to large concentrations of barges or shipping and to aerodromes likely to be used by German striking forces bound for the United Kingdom. The outcome of these frequent changes, and of the latitude which even the firmest of the directives conferred on Air Marshal Portal, was that in practice only about 47 per cent, of the tonnage dropped by Bomber Command in July and August was aimed at the German aircraft industry and aerodromes, rather more than 13 per cent, at barges, ships and naval targets, and the rest at oil targets and communications.58 The fighter force took part in a few attacks
on aerodromes recently vacated by the Advanced Air Striking Force, but were soon fully occupied on their own side of the Channel.
By the third week in June about 150,000 civilians, besides troops, were engaged on. the defensive works required by the new plan of defence on land.59 Notwithstanding the hope that victory in the air might postpone or even preclude invasion, the task was undertaken in a spirit of great urgency. The consequent allotment of much of the work to civilian contractors without experience of military engineering led to many blunders. A large number of road-blocks proved useless, as armoured vehicles could go round them; some pillboxes were sited facing the wrong way, or so placed that they could not be occupied by troops or served no useful purpose.60 A more radical objection was that the garrisoning of so widespread a system of static lines, in addition to large numbers of 'vulnerable points', left too few troops available for counter-attacks and threatened to direct attention too exclusively to purely defensive measures. Divisional commanders, finding that the manning of the stop-lines would consume most of their manpower, and knowing that even in favourable circumstances reinforcements could not reach them in less than twelve hours, were worried by the smallness of their local reserves and their consequent inability to take offensive action.61 Ironside, who would himself have liked nothing better than the opportunity to frame a more offensive strategy, admitted that the plan left fewer troops in local reserves than could be wished. But he pointed out that, as most of the forward divisions had little artillery or transport, and were not fully trained, their ability to counter-attack would be small in any case.62
Even so the plan was widely criticised. The Vice-Chiefs of Staff maintained that to make no major attempt to halt the enemy until a great part of the country had been overrun was a suicidal policy.63 The Chiefs of Staff, while conceding that Ironside's dispositions met the requirements they had laid down, agreed that the balance of the defence leant too far on the side of a thinly-held crust on the coast, with insufficient mobile reserves in immediate proximity to points where penetration must be expected.64 The Naval Staff (some of whose opinions applied also to later plans) were made uneasy by the thinness of the crust near Dover, where lack of room for big, ships to manoeuvre might offset the German lack of surface strength.65 Finally, airmen were far from content with the arrangements made for the defence of aerodromes.66 Believing that at vital air bases everything
Organisation for Home Defense, Summer, 1940
should be done to prevent airborne forces from gaining even a temporary foothold, the Air Staff had urged on General Kirke in May that local guards should be supplemented by first-class troops generously supplied with automatic weapons.67 But he and his successors argued that the comparatively few trained troops available were better employed as counter-attack formations, so placed as to be able to arrive within two to three hours of an alarm.68 ln the outcome the local guards were supplemented in June by parties of airmen armed with rifles, and open lorries were fitted with Bren guns as a means of dealing rapidly with airborne troops or parachutists who /might descend in awkward places, such as the centre of a landing-area.69 The value of these additions was debatable, if only because they might tend to divide or at least confuse responsibility.
Mr. Churchill's views lent only partial support to the Vice-Chiefs of Staff. In his estimation the strength of the defences on a given stretch of coast must be measured, not by the number of troops immediately available, but by the number of hours within which strong counter-attacks could be delivered.70 It ought, in his opinion, to be possible to concentrate 10,000 well-armed men within six hours, or twice that number within twelve hours, at any point where the enemy had come ashore in strength. He suggested that groups of 'Storm Troops' or 'Leopards', drawn from existing units, should be held ready to pounce within four hours on the points of lodgement, and that their aggregate strength should be not less than 20,000 men. In his view everything would turn on the 'rapid, resolute engagement' of all parties landed. Rapid, resolute engagement should, he added, not be beyond the power of Home Forces as long as their field troops were not consumed in beach defences, but kept in a high state of mobility.
To such criticisms of the plan he had made in June, Ironside could return the simple answer that at that time the trained troops and material resources needed to give the defences a more mobile and more offensive character did not exist. As he put it later: 'The Army had not been trained to take the offensive: to create an offensive spirit suddenly, with no mobility, no armour and no training, was impossible.'71 But as the weeks went by, a respite from German interference, and above all the efforts of our war-factories, created opportunities for improvement.
It fell to General Sir Alan Brooke, who succeeded Ironside on 20th July, to give a more offensive cast to the defences. More fortunate than his predecessor, he set to work at a time when vehicles and weapons were not quite so scanty. Early in August he proclaimed his intention of stamping out the idea of linear defence and making 'mobile offensive action' the keynote of his strategy.72 Hence-forth the stop-lines would take second place, and local mobile
reserves would be held within reasonable striking-distance of likely landing-places.
Accordingly, in July and August divisions in G.H.Q. Reserve moved forward into Cambridgeshire, Hertfordshire and Surrey, taking up positions about half as far from the coast as those they had occupied in June. General Brooke ordered that work on the stop-lines should be limited to the formation of nodal points for all-round defence at important road-junctions and centres of communication, and that their garrisons should be withdrawn to strengthen local mobile reserves.73 In an emergency the nodal points would be manned by any troops who happened to be near them. His anti-tank guns, formerly mostly in rear of the G.H.Q. line, he moved forward to cover beach obstacles and debouchments from the beaches. Field artillery returned to a mobile role, and heavy guns were sited within range of likely landing-places for seaborne and airborne troops. But even when these changes had been made, Brooke's forces were still far short of the mobility and offensive power which would have given them a comfortable prospect of success if the Germans had landed a substantial armoured force.
Meanwhile the fixed defences had been greatly strengthened. A screen of coastguards and coast-watchers covering the whole coast now stood behind the system of naval and air reconnaissance patrols. Finally, a growing array of minefields (see Map 9) guarded the approaches to the stretches of coast best suited to a landing.
The respite gave time, too, for improvement of the means of concerting military and civil plans. As an executive body, the Home Defence Executive set up in May proved unwieldy.74 Retaining its old name, it became in June a co-ordinating body under the chairmanship of Sir Findlater Stewart, an experienced civil servant who acted also as Chief Civil Staff Officer to the Commander-in-Chief, Home Forces.75 Henceforth executive measures were initiated either from G.H.Q,., Home Forces, at St. Paul's School, Hammersmith, or from the offices of the departments most concerned. The Chief Civil Staff Officer provided the link between G.H.Q. and the departments, but was much more than a liaison officer. Under his guidance new arrangements were made to avoid the hasty flight of refugees which had caused so much distress and confusion in Continental countries. By the middle of July 127,000 people, or nearly half the population, had left East Anglian coast towns under voluntary schemes and special arrangements made for children and old people; similarly some 80,000, or roughly two-fifths of the population, moved inland from coast towns in Kent.76 Those who remained were warned that, if invasion came, they would be expected to stay where they were till further orders, so that the roads could be kept clear for military traffic. If their withdrawal became necessary, it would be done under
the orders of local commanders, who would be advised by the appropriate Regional Commissioners. Far-reaching arrangements for denial of commodities to the invader now included the thinning-out of petrol pumps at garages in coastal areas from the Moray Firth to the Bristol Channel, and detailed plans for the destruction in an emergency of those left in working order.77
The system of command was also reviewed. One effect of the national danger was to revive an old demand for a supreme commander wielding authority over all branches of home defence. At the time, the arguments for that course seemed less compelling than they may appear in retrospect. The Chiefs of Staff concluded early in July that, even if the right man to exercise so grave a responsibility could be found, he would need help from an integrated staff whose creation would 'superimpose a cumbersome and top-heavy incubus' on the existing staffs of the fighting services.78 Accordingly, the system outlined in Appendix III remained in force, with such modifications as the times made necessary. The Commanders-in-Chief or Flag Officers commanding the naval home commands continued to be directly responsible to the Admiralty, the Commanders-in-Chief of the metropolitan air commands to the Air Ministry. The Commander-in-Chief, Home Forces, controlled all troops in Great Britain, except anti-aircraft units and such special formations as the Free French Contingent. Under a system set up in May, each of the chief army commands was given the status and staff of an Army Headquarters and (except for Scottish Command) passed orders through one or more Corps Headquarters, according to the number of divisions in its area. Forces in Northern Ireland and Iceland remained under the War Office, but once the country was invaded all troops in the United Kingdom (again excepting Anti-Aircraft Command) would be controlled by General Brooke or his successor. Liaison officers at various formations, complemented by senior naval and air officers attached to G.H.Q. at Hammersmith, kept the Commander-in-Chief, Home Forces, in touch with the sister-services, while the Area Combined Headquarters, and the special status of the Commander-in-Chief, Coastal Command, as air adviser to the Admiralty, provided links between the naval and air branches of maritime defence. In view of his exceptional responsibilities, the Commander-in-Chief, Home Forces, was given direct access to the Government, and set up an Advanced Headquarters close to the Cabinet War Room, where he and his senior officers would be available for consultation by ministers and the Chiefs of Staff if invasion came. Early in the war arrangements had been made to move the War Cabinet and government departments to the West of England in an emergency; but as that part of the country was no longer virtually immune from air attack they were abandoned, and premises reserved
for the purpose were used to house staffs which did not need to be, or could not be, accommodated in the capital. Should the Germans land, the War Cabinet, the Chiefs of Staff and the Naval, General and Air Staffs would stay in London. If driven from Whitehall, they would move to duplicate War Rooms in the suburbs.
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