The Night Offensive Against London*
(7th September-13th November, 1940)
THE OPENING of the air offensive against London on 7th September, 1940, marked not only a change of target for the Luftwaffe, but also the beginning of a change in policy which ultimately transformed its operations against this country. Experience had taught the German Air Staff that mass attacks in daylight brought heavy losses, but that big night raids like those on Liverpool and Birkenhead in August could be made at little cost. They applied the lesson. Without altogether abandoning attacks in daylight--which continued into the winter on increasingly rare days of good weather--they soon reduced the scale of their day-bomber operations after trying a few mass attacks on London. Thereafter the bulk of their effort went into night attacks. Both Luftflotten in France and the Low Countries shared in the night raids, aiming about 5,300 tons of high-explosive at London and its outskirts on twenty-four nights in September, or more than four times the load dropped in daylight during the same period.1
Although not primarily designed for a night offensive, the German bomber force was by no means ill equipped for such a task. Like the British Blenheim (but unlike the heavier bombers which the Royal Air Force was introducing in increasing numbers), its aircraft carried a modest load and owed their genesis to an exploded faith in their ability to outpace pursuing fighters. But in the aggregate their striking-power was considerable. Between them Luftflotten 2 and 3 mustered in early September more than seven hundred serviceable bombers, each capable of carrying well over a ton of bombs across the Channel. Captured aerodromes in occupied countries provided a string of bases so widely distributed that all were scarcely likely to be weatherbound at once. Finally a lavish array of beacons, beam-transmitters and other aids to night-flying and target-finding made night-raiding possible in weather which greatly hampered the defences.
At best the resources available in the United Kingdom to meet the threat were meagre. After the first night raid on London, General
* For statistical summaries, see Appendices XXVI-XXVIII.
Pile received authority to raise the number of heavy anti-aircraft guns in the inner artillery zone from 92 to 199, largely by drawing on the Midlands and on South and East Coast ports; but lack of adequate equipment for directing 'unseen' fire made them capable of little more than wild shooting, comforting to the ears of Londoners and doubtless disturbing to some bomber-crews, but unlikely to bring down many aircraft. The removal, on 11th September, of restrictions which forbade the gunners to fire except at aircraft specifically seen or detected led to a system of barrage-fire which, however unlikely to bring a high proportion of successful engagements, nevertheless had certain merits. The radio counter-measures controlled by No. 80 Wing--which included by October fifteen equipments to counter KNIKCEBEIN, besides the transmitters already installed to counter medium-frequency beacons*--were a potent asset, but their value was partly discounted by the comparative ease with which so large a target as London could be found without recourse to artificial aids. Balloons, like barrage-fire, were useful chiefly as a means of keeping the enemy high and were seldom lethal. As for night-fighters, Dowding's resources in September comprised only some eight squadrons which could be properly so called.† Six Blenheim squadrons were divided between the four fighter groups, with two in No. 11 Group near London and two in No. 12 Group, while one Defiant squadron was in No. 12 Group and the other divided between Nos. 11 and 13 Groups. Elements of a large number of single-seater squadrons were nominally available each night to swell the total, but only half a Hurricane squadron in No. 10 Group claimed any special aptitude. Air Vice-Marshal Brand, commanding that group, had gained distinction in the First World War as a night-fighter pilot in single-engined aircraft, so that he had a special interest in the matter; elsewhere the prevailing opinion was that the slender chance of intercepting bombers in the dark with ordinary day-fighters scarcely justified their diversion from normal duties unless conditions were exceptional. In addition, one section of the specially-equipped Fighter Interception Unit--the pioneers of airborne radar--was available in Sussex.
At the beginning of the night-battle, therefore, success seemed likely to turn on the speed with which night-fighter squadrons proper could be given the tools to do their job. Modern equipment for the guns was also an urgent need, but the inherent difficulty of gunfire against unseen targets made the chances of the fighters seem more promising. The immediate outlook, however, was not good. The Blenheim, designed originally as a bomber, was too slow for the work; its successor the Beaufighter was only just coming into service and was abnormally beset by teething troubles.2 Airborne radar was
* See p. 158.
† For details, see Appendix XXIX.
now at an advanced stage of development; but its use and maintenance on active service raised many problems. Moreover, the equipment was valueless without some means of bringing aircraft which carried it within working distance of their quarry. In average conditions a fighter which relied on airborne radar had to get within about three miles of its objective to establish contact; thereafter the pilot and radar operator, working in partnership, used the apparatus to close the range until the bomber or its exhaust flames became visible. Information furnished by the Observer Corps was seldom accurate enough for the purpose, especially in regard to height; while fighters patrolling fixed lines had only a remote chance of success. A more promising method was to station fighters over landmarks known to be favoured by the enemy; but in practice even this proved disappointing. Over the sea the data furnished by ordinary radar stations could be used, but here too accuracy was not easily attained. Moreover, there were objections to the use of aircraft fitted with highly secret apparatus at any considerable distance from the coast. When the enemy was using beams, patrols along the beams by fighters equipped to receive their message seemed likely to be profitable; but German crews perceived the danger and grew wary. Searchlights could of course be used to point the way for fighters if they themselves could find the bombers; but without new equipment they stood little chance of doing so. What the fighters and the searchlights needed was assistance from some form of radar on the ground which would reveal, with much greater accuracy than sound-locators or similar devices, the course and height of bombers flying almost directly overhead.
As it happened, a radar set which satisfied these conditions already existed under the name of the G.L. set. For some time past the War Office had been developing a gun-laying equipment which was capable of accurate tracking within vertical or slant ranges of 40,000 feet and of estimating height to within a thousand feet or so of the true figure.3 At the cost of further retarding the progress of the guns--for the equipment was still scarce--Dowding borrowed a number of the sets and installed them experimentally at searchlight posts in the Kenley sector, on the path most commonly used by night-bombers flying towards London. Direct communication with Kenley enabled these searchlight posts to keep the sector controller informed of the course and height of bombers in their neighbourhood. The controller, who was made aware of the position of his own aircraft by the means used for daylight interception, then had the task of bringing a selected fighter within range of a selected bomber, partly by verbal orders given by radio-telephony and partly by ordering a 'master' searchlight to point towards the indicated position of the bomber. The method was ingenious and formed the basis of the more elaborate technique adopted later when special 'G.C.I.' equipment for the
ground control of interception at night came into service. But its application in the early stages proved very difficult. Working in an operations room designed with other needs in mind, and burdened with multiple responsibilities, the sector controller had an unenviable task. Redhill, the only aerodrome available for night-flying in the Kenley sector, was ill adapted for the purpose, especially in wet weather; damp and inexperience played havoc with delicate airborne radar sets which at best were apt to give capricious readings. Fighters were sometimes incorrectly tracked, or even confused with the bombers they were chasing; communication between pilots and radar operators was sometimes interrupted by untimely orders from the ground. And when the airborne radar did pick up the quarry the Blenheims were usually too slow to catch it, while the Beaufighters which were gradually replacing them gave much trouble until a variety of technical ills were remedied. The outcome was a tantalising series of missed chances in the form of radar contacts broken off before the quarry came in sight. Indeed, if German reports are to be believed, the crews of bombers saw our fighters far more often than their own machines were seen.4
In any case the Kenley experiment was confined to a single sector. Even if it were successful, not enough G.L. sets existed or could be manufactured within a foreseeable time to make the system widely applicable.5 A simpler variant, expressly designed for the control of searchlights and known as S.L.C., was on the way, but suffered from defects which proved extremely hard to overcome. In the upshot only the special G.C.I, equipment designed from the outset to help fighters filled the bill, but the sets would not be available in substantial numbers before the end of 1940. By that time, too, the supply of G.L. sets might be expected to benefit the guns. The question was, what could be done to check the bomber effort in the meantime?
This problem, among other aspects of night air defence, was discussed in September by a committee set up by the Air Council under Marshal of the Royal Air Force Sir John Salmond, a veteran officer of great distinction. The committee's findings were largely concerned with the development of airborne radar on lines discussed in the foregoing paragraphs; but they also recommended that more attention should be paid to single-seater aircraft as night fighters.6 A little earlier Air Vice-Marshal W. S. Douglas, a member of the Air Staff whose duties were largely concerned with air defence, had urged that not only the two existing Defiant squadrons and a third Defiant squadron then in process of formation, but also a Hurricane squadron, should be devoted exclusively to night-fighting.7 Believing that fighters without airborne radar--which could not then be fitted in single-seater aircraft, though Douglas was given to understand that the difficulty might soon be overcome--could accomplish little
in the dark until the searchlights were better equipped, Dowding dissented from the last suggestion.8 The report of the Salmond Committee gave fresh support to the view expressed by Douglas; and early in October the Chief of the Air Staff, having discussed the matter with the Prime Minister, ordered Dowding to relegate no less than three Hurricane squadrons to night duty.* To Dowding this move seemed unwise. Convinced that the future of night interception lay with airborne radar and that 'haphazard methods' would never produce more than 'an occasional fortunate encounter', he obeyed the order with great reluctance, conveyed to his superiors in a trenchant protest.9 Douglas and other members of the Air Staff remained of the opinion that attempts to intercept at night with single-seater fighters were, at any rate, well worth making.
Another suggestion made by the committee and supported by the Air Staff was that separate Filter Rooms--already existing in Nos. 9 and 10 Groups--should be opened at each group headquarters in place of the Central Filter room at Stanmore.† Here too Dowding dissented, and here too he was overruled. Not all the arguments adduced by the Air Staff in favour of devolution were well founded; but the view that dangerous congestion at Stanmore would thereby be avoided was probably justly held to outweigh, Dowding's objections, based largely on considerations of expense.10 For reasons too technical to be discussed here, devolution of filtering strengthened an existing case for a similar devolution of responsibility for initiating air-raid warnings, so that this too followed in due course.11 In 1941 separate Filter Rooms were opened at the headquarters of Nos. 12, 13 and 14 Groups and of the new No. 82 Group in Northern Ireland. Experimental devolution of responsibility for initiating air-raid warnings to Nos. 9 and 10 Groups was followed by devolution to Nos. 12, 13, 14 and 82 Groups. Filtering for No. 11 Group continued to be done at Stanmore (ultimately in a room outside command headquarters); and warnings to the area covered by that group were still issued and cancelled from the command operations room until, in 1944, the Ministry of Home Security assumed responsibility for initiating warnings to all parts of the country.‡
These changes had little or no immediate effect on the performance of the night defences, though they served to emphasise important differences of outlook between Dowding and the Air Staff. Whatever the ultimate value of the Hurricane squadrons as night-fighters, they could scarcely hope to accomplish much in such conditions as must
* The squadrons chosen were Nos. 73, 85 and 151. In November, No. 73 Squadron was transferred to the Middle East and No. 87 Squadron took its place.
† Filtering was the term applied to the collation of information from radar stations so as to produce a continuous track for each aircraft identified as hostile.
‡ For a further account of the development of the public warning system, see T. H. O'Brien, Civil Defence (1955), pp. 425 and 435 and passim.
be expected on many nights throughout the winter. As for devolution of the filtering and air-raid warning systems, they would take some time to put into effect, and in any case had little bearing on the immediate issue. By early November two twin-engined squadrons, in addition to the Fighter Interception Unit, had some Beaufighters to supplement their Blenheims, but air and ground crews were still not quite at home with them. In the middle of October the first of the new G.C.I, equipments was experimentally installed in Sussex, but further deliveries were not expected until Christmas.12 By October, too, a few G.L. sets had reached the gunners, who pronounced them far superior to anything within their previous experience.13 As early as September, No. 80 Wing had reported that their counter-measures were at least effective enough to make the Germans alter their call-signs at irregular intervals.14 But solid progress in the shape of a substantial number of bombers brought down was still lacking. On the other hand, as the year drew to its close the German bomber force suffered fairly heavy losses from accidents for which the night defences, whose efforts must certainly have increased the strain on pilots, can fairly claim some credit.15
Meanwhile, from the end of the first week in September until the middle of November London was attacked nightly by an average of about a hundred and sixty German bombers.* The only respite came on the night of 3rd November, when prohibitive weather over England and a great part of the Continent confined the Luftwaffe to objectives in Scotland. For similar reasons only a handful of bombers attacked London on the night of 6th October, and on eight other nights the number attacking did not exceed a hundred. According to German records about 6,500 tons of high explosive were aimed at London and its outskirts by. night in October and some 1,800 during the first half of November.16 Other places--notably Liverpool, Manchester, Birmingham and Coventry--received their share; but for ten weeks Greater London was the main objective.†
* For details, see Appendix XXVI. Italian bombers contributed to the offensive from October, making 16 night sorties in that month and 8 in the first half of November. The Italian contribution by day and night is set out in Appendix XXVIII.
† According to German sources the bomb-load for October (day and night together) was distributed as follows:
Tons of H.E. Incendiary
Greater London 7,160 4,735 Liverpool and Manchester 220 369 Birmingham (18th onwards) 217 591 Coventry (19th onwards) 17 332 Aerodromes 190 165 Ports and shipping 352 355 Aircraft industry (51 targets) 63 81
A British source puts the total tonnage dropped on the United Kingdom in October at 6,910, of which 5,854 tons were dropped at night. But there are grounds other than the German figures for thinking these estimates too low.
Damage extended to almost every borough, but was most severe in districts near the river. Docks, railways and public utilities suffered badly and many commercial and domestic buildings were destroyed. Interference with rail traffic was so great that at one stage the Great Northern section of the London and North-Eastern Railway could pass only four trains a day to the Southern Railway instead of the usual fifty or sixty; in September five or six thousand wagons stood idle because their passage was blocked by unexploded bomb.17 In dockland many warehouses were destroyed with their contents, and in numerous districts damage to gasworks and power-stations caused much inconvenience. Injuries to life and limb, though sufficiently distressing, were lighter than had been foretold before the war; but throughout the capital new dangers and difficulties shattered the orderly routine of millions. On one night in October--that of the 15th, when more than four hundred bombers aimed nearly 540 tons of high explosive at Greater London--damage to railways caused temporary stoppage of all services at St. Pancras, Marylebone, Broad Street, Waterloo and Victoria, while at Euston, Cannon Street, Charing Cross and London Bridge traffic was reduced to less than a third of the normal volume. The District Railway, which carries thousands of Londoners to and from their daily work, was cut at three widely-separated points; on the Metropolitan Railway Baker Street and Moorgate stations were put out of action. No trains ran between Edgware Road and South Kensington. A bomb on the outskirts of the City burst the Fleet sewer, whose waters poured into the tunnel between Farringdon Street and King's Cross. Tube railways were likewise severed at many places where they ran above ground; elsewhere access to them was barred at several points by damage to stations or the proximity of unexploded bombs or mines. Roads were blocked in whole or part at seven or eight places, from East Ham in the east to Fulham in the west, and as far north and south as Tottenham and Lewisham; for some hours Oxford Street was closed and London Bridge open only to southbound traffic. Damage to public utilities included the fracture of three large water-mains; in addition a reservoir, three gasworks, two power stations, three dock areas and the headquarters of the British Broadcasting Corporation in Portland Place all suffered hits. Altogether more than nine hundred fires were reported in the London Region, including six afterwards described as 'major' and nine as 'serious'. And during the night's bombing, which lasted from dusk until nearly five o'clock next morning, more than four hundred civilians were killed and nearly nine hundred seriously injured. About two hundred people perished while seeking asylum in shelters or rest-centres. Many Londoners were rendered homeless, some losing all or most of their possessions.
Nevertheless the two months' offensive against London failed to do
mortal injury to the British capital. The blow struck at the docks, said the Ministry of Home Security in an objective study, was 'serious but not crippling'.18 ln the main the basins, quays and gates, and the equipment and railway lines which served them, remained substantially intact; and in the long run the ability of the Port of London to handle the imports and exports needed to keep the capital and the country going was not much impaired. Wise dispersal of stocks of food to depots away from the docks reduced the effects of damage to dockland buildings; damage to communications, power stations and the like was seldom lasting. Under the direction of a Special Commissioner appointed for the purpose, roads and public utility undertakings were repaired with creditable speed, despite the hindrance of rubble and salvage often difficult to clear. Another Commissioner supervised the bestowal of the homeless and the needs of those not tied to London who sought a roof elsewhere. The menace of the delayed-action and the unexploded bomb was met by the formation of reconnaissance and disposal parties--among whose notable feats were the removal of a one-ton bomb which threatened St. Paul's Cathedral--and the establishment of 'bomb cemeteries' for the reception of their merchandise. Naval parties under the Admiralty dealt with land-mines dropped by parachute from German aircraft.
Concerning the attitude of Londoners the Ministry of Home Security 'had only good report.19 Criticism of the small volume of gunfire noticeable at the beginning of the night attacks was met by measures mentioned earlier in this chapter; for if the guns added to the inner artillery zone could accomplish little without new equipment, at least they made a joyful noise and served to mask the desolating drone of German engines. In frequent peril, deprived of many familiar comforts, often short of sleep and sometimes of hot food and water, compelled if they went out after dark to find their way with feeble torches through a gloom relieved at times by the glare of fires, the flash of bombs and guns or the pale gleam of an unwelcome moon, dwellers in London endured much during the long nights of the deepening winter. Yet the public temper, strengthened by the resolute but wisely cautious tone set by the Prime Minister in broadcast commentaries, remained firm. If conditions were hard--and by urban standards they were sometimes very hard indeed--life was still sweet to those who faced the nightly peril of maiming or extinction. Danger and discomfort left much room for dogged humour, for a new sense of fellowship between all classes, even for gaiety. Some months earlier, on the eve of Dunkirk, the Chiefs of Staff had said that, if the nation and the Empire were to endure, 'the gravity of the problem and the need for individual self-sacrifice' must be brought home to the people.20 For millions of
Londoners the night offensive of 1940, perhaps much more than the earlier peril of invasion, performed that function, steeling them for the long years of slogging war that lay ahead. And the turn of their neighbours in the provinces was close at hand.
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