Area Bombing Begins

Night navigation in 1941 depended on forecast winds, dead reckoning, visual landmarks and occasional radio bearings. Cloud could hide the coast, rivers and cities; blackout removed many of the lights crews had used in peacetime; and fires, searchlights and decoys could make a wrong town look convincing. The bombing camera was therefore crucial because it recorded the ground beneath the aircraft at release rather than the place the crew believed it had reached.

David Bensusan-Butt examined roughly 650 usable night photographs from raids in June and July 1941. Of aircraft recorded by their crews as attacking the assigned target, only about one in three had come within five miles of the aiming point. Over Germany the figure was about one in four and over the Ruhr about one in ten. The report also stressed how generous that test was: a circle five miles from the aiming point covered more than seventy-five square miles, much of it open country, and only about two-thirds of all sorties dispatched had even been recorded as attacking.

The Ruhr combined nearly every difficulty in one place. Industrial haze obscured the ground, adjacent towns merged into a continuous urban belt, and the approaches were covered by radar, searchlights, anti-aircraft guns and controlled night fighters. A crew that reached the Ruhr was still left with the harder problem of deciding which part of it lay beneath the aircraft.

Gee changed navigation from March 1942 by giving crews timed radio fixes and helping a force arrive in the same region together. It did not turn a night bomber into a precision weapon. The first Gee-supported attack on Essen reached the Ruhr on time but scattered onto neighbouring towns and left Krupp's works virtually untouched; a few nights later better visibility helped produce a more concentrated attack on Cologne. The difference between those two raids showed what would govern the campaign for the rest of 1942: electronic navigation could bring the force close, but weather, visual identification and target marking still decided where the bombs actually fell.

The Butt Report did not create the accuracy problem, and the Area Bombing Directive was not a single automatic response to it. Bomber Command had already been debating how a force that could rarely identify a factory at night should be used. The argument became more urgent after the night of 7 November 1941, when thirty-seven bombers were lost from a force of about four hundred attacking Berlin, Mannheim, the Ruhr and other targets. A conservation directive followed on 13 November while the command rebuilt and waited for Gee to become available in useful numbers.

On 14 February 1942 the Air Ministry authorised a renewed offensive and made the morale of the enemy civil population, particularly industrial workers, the primary focus. The target system was concentrated on the industrial cities of western and north-western Germany that lay within Gee range. Air Staff correspondence also made the aiming-point rule explicit: where a city contained named factories, dockyards or other installations, the general aiming point was still the built-up area rather than the individual plant.

Arthur Harris took command on 22 February. He had not drafted the directive, but he agreed with its central operational premise that the force available to him could not systematically find and destroy small industrial objectives at night. That distinction matters. The policy came from the Air Staff and War Cabinet; Harris's role was to turn it into a sustained method and later to resist attempts to move Bomber Command away from area attack.

The argument was also about resources. Frederick Lindemann's dehousing memorandum of 30 March did not create the February policy; it tried to quantify what a much larger bomber force might accomplish by destroying urban housing and displacing workers. Patrick Blackett and other critics challenged the assumptions and argued that aircraft, crews and production could yield more immediate returns elsewhere, especially in the Battle of the Atlantic. Operation Millennium became part operational experiment and part institutional demonstration: if Bomber Command could put a thousand aircraft over one city in a short period, it could test the German night-defence system and make the case for expansion with results visible from the ground.

When Harris arrived, Bomber Command was still dominated by Wellingtons, Whitleys and Hampdens. Stirlings, Halifaxes, Manchesters and the first Lancasters increased bomb lift, but the official history records only sixty-nine heavy bombers serviceable with crews on the day he took command. The thousand-bomber raid therefore depended less on a new aircraft than on temporarily assembling almost everything that could fly, including hundreds of machines from the training organisation.

The new technology solved different parts of the problem. The F.24 camera provided independent evidence of where crews had released their bombs. Gee improved route keeping and concentration, but did not identify a factory through cloud or haze. On the German side, Freya and Würzburg radar, searchlights and ground-controlled night fighters were organised into interception sectors. That system could deal effectively with bombers arriving in dispersed streams, but its capacity was limited when hundreds of aircraft were pushed through the same corridors on a strict timetable.

The bomb load was also being adapted to an area target. Four-pound incendiaries could scatter thousands of separate ignition points across a built-up district, while high-capacity bombs opened roofs, damaged utilities and disrupted firefighting. By spring 1942 the Air Staff and Harris had settled on a normal mixture weighted heavily toward incendiaries rather than either weapon being used alone. Lübeck showed how destructive that combination could be against a vulnerable old city; Essen showed that the same load was of little use when the force could not first establish where the intended city centre actually was.

The raid on Lübeck killed about 320 people. Modern municipal accounts put the number of buildings completely destroyed at roughly 1,500 and the number made homeless at more than 15,000; the RAF official history, reproducing a wartime German return, gives 1,918 buildings completely destroyed. The difference is a reminder that even apparently precise damage totals depend on which contemporary or later accounting system is being used.

Cologne produced a better-documented contemporary return. The police report reproduced in the RAF official history recorded 486 deaths, 5,027 injuries and 59,100 people made homeless. Forty of the 1,046 aircraft in the main bomber force failed to return, while two more were lost from the supporting intruder operations. The raid demonstrated that a concentrated stream could overwhelm the existing night-defence system, but it did not make mass operations cheap.

Germany answered the Baltic raids with the Baedeker campaign against historic British cities. Exeter, Bath, Norwich, York and Canterbury were attacked during the spring and early summer of 1942, killing about 1,600 civilians across the campaign. The reprisals did not reverse British bombing policy, but they made the reciprocal targeting of urban populations explicit on both sides.

The final thousand-bomber raid of this period, against Bremen on 25–26 June, cost forty-nine aircraft. Harris still hoped to mount two or three very large raids each month, but weather, rising losses and damage to the training system prevented it. The method of concentrating a bomber stream had been demonstrated before Bomber Command possessed the force, navigation aids or specialist target-marking organisation needed to repeat it routinely.

The chronology is anchored in the officially commissioned RAF history and the Air Historical Branch campaign narratives for the bombing offensive. These records are particularly useful for the Butt Report, the November 1941 losses, the February directive, the Gee trials, the Baltic raids and the planning and results of Operation Millennium.

The Butt Report and Air Ministry directive survive in the Cabinet and Air Ministry files at Kew. Cologne's casualty and damage figures come from the German police report reproduced in the official history. Lübeck is cross-checked against modern municipal records because the surviving totals for destroyed buildings are not identical. The Baedeker section uses British civil-defence records and Historic England's work from the relevant National Archives files.