Circumventing the law that humans cannot see in the dark: an assessment of the development of target marking techniques to the prosecution of the bombing offensive during the Second World War Submitted by Paul George Freer to the University of Exeter as a thesis for the degree of Doctor of Philosophy in History in August 2017 This thesis is available for Library use on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. I certify that all material in this thesis which is not my own work has been identified and that no material has previously been submitted and approved for the award of a degree by this or any other University. Signature: Paul Freer 1 ABSTRACT Royal Air Force Bomber Command entered the Second World War committed to a strategy of precision bombing in daylight. The theory that bomber formations would survive contact with the enemy was soon dispelled and it was obvious that Bomber Command would have to switch to bombing at night. The difficulties of locating a target at night soon became apparent. In August 1941, only one in three of those crews claiming to have bombed a target had in fact had been within five miles of it. And yet, less than four years later, it would be a very different story. By early 1945, 95% of aircraft despatched bombed within 3 miles of the Aiming Point and the average bombing error was 600 yards. How, then, in the space of four years did Bomber Command evolve from an ineffective force failing even to locate a target to the formidable force of early 1945? In part, the answer lies in the advent of electronic navigation aids that, in 1941, were simply not available. By 1945, electronic aids such as GEE, Oboe and H2S were widely in use. Secondary literature on the bombing offensive tends to attribute the improvement in bombing performance to the introduction of these aids. However, the introduction of these aids was only part of the story. These aids could not, in themselves, circumvent the law that human beings cannot see in 2 the dark. Having reached the target area with the benefit of navigation aids, some form of identifying the Aiming Point was necessary if the target was to be accurately bombed. Part of the reason for the effectiveness of Bomber Command by early 1945 therefore lies in the development of techniques for the identification and marking of targets. Although the development of navigation aids is well documented, the development of techniques for target marking has received much less attention. The aim of this thesis is to examine this largely neglected aspect of the bombing offensive. The key question asked is: what difference did the introduction of target marking techniques make to the performance and efficacy of Bomber Command? 3 CONTENTS Abstract List of Tables and illustrations Definitions and Abbreviations Introduction Chapter 1: Before target marking Chapter 2: Blind bombing Chapter 3: Early target marking techniques Chapter 4: The formation of the Pathfinder Force Chapter 5: Pathfinder Force techniques Chapter 6: No 5 Group target marking techniques Chapter 7: The role of the Master Bomber Conclusion Glossary Bibliography 99,270 words, excluding Abstract, Bibliography, Glossary, and footnotes. 4 LIST OF TABLES AND ILLUSTRATIONS Tables Table 1/ Butt Report: target groups Table 2/ Butt Report: the 9 states of visibility Table 3/ Butt Report: effect of cloud cover Table 4/ ORSBC Report: features given by crews as means of target identification Table 5/ ORSBC Report: percentage of aircraft within target area by number of features identified Table 6/ ORSBC Report: Effectiveness of specific ground features in identifying targets Table 7/ ORSBC Report; percentage within target area Table 8/ ORSBC Report: percentage of aircraft that attacked ‘useful’ areas Table 9/ Relationship between Probable Radial Error using H2S and mean radius of German towns Table 10/ Comparison of marking techniques used for attacks on marshalling yards Table 11/ Comparative accuracy of target marking techniques Illustrations Fig 1/ Butt Report: Percentage of photographs within the target area Fig 2/ Butt Report: Percentage of photographs within the target area by target type 5 Fig 3/ Butt Report: Percentage of photographs within target area by state of visibility Fig 4/ Butt Report: Percentage of photographs within target area by cloud and phases of the moon Fig 5/ ORSBC Report: Effectiveness of specific ground features in identifying targets Fig 6/ ORSBC Report: Comparative charts for June - Nov 1941 and Dec 1941 - Feb 1942 Fig 7/ ORSBC Report: Distribution of plotted photographs around the target Fig 8/ Percentage of photos taken with bombing showing useful targets in relation to villages & outskirts and open country Fig 9/ GEE Lattice chart Fig 10/ GEE Coverage Fig 11/ Hypothetical 50% GEE ellipse Fig 12/ Map showing standard deviation from the GEE co-ordinates of bombs dropped using GEE as a blind bombing device Fig 13/ The Oboe principle Fig 14/ H2S: The reflective qualities of different surfaces Fig 15/. H2S: Plan Position Indicator Fig 16/ The effect of reduced wavelength on image resolution Fig 17/ The "H principle" or "twin-range principle" of location determination Fig 18/ Typical attack profile using G-H Fig 19/ Illustration of errors in track keeping on a G-H attack Fig 20/ Principle of Skywave Synchronization Chain Fig 21/ Gaussian Distribution Function curves for bomb distribution Fig 22/ Bomb distribution plot for the raid on Barmen-Wuppertal, 29/30 May 1943 Fig 23/ Bomb distribution plot for the raid on Hamburg, 24/25 July 1943 6 Fig 24/ Bomb distribution plot for the raid on Hamburg, 27/28 July 1943 Fig 25/ Principal landmarks in and around Berlin Fig 26/ Mean Gaussian Distribution curves for attacks of Marshalling yards using Musical Parramatta Fig 27/ Improvement in efficiency (accuracy) of Bomber Command night attacks August 1942 to April1945 Fig 28/ Timing chart for the raid on Kassel, 22/23 October 1943 7 DEFINITIONS AND ABBREVIATIONS Definitions Aiming Point The point on the ground that is the briefed target for the raid. Blind Bombing Release of bombs without visually identifying the target, using navigation aids to determine position. Estimated Weight of Attack The minimum weight of attack necessary to destroy the social and industrial structure within selected areas (towns), measured in tons of bombs per square mile or tons of bombs per population number. Mean Point of Impact The mathematical centre of the bomb distribution. Point of Aim A point on the ground, marker or pattern of markers on which the Main Force were briefed to aim. Probable Radial Error Radius of a circle about the Aiming Point or the Mean Point of Impact within which 50% of the plotted bomb distribution are located. Random Error The measure of bomb scatter about the Mean Point of Impact Systematic Error The distance of the Mean Point of Impact from the Aiming Point, measured as a direct line. Abbreviations A&AEE Aircraft and Armament Experimental Establishment A/C Aircraft ACAS Assistant Chief of Air Staff ACAS (Ops) Assistant Chief of Air Staff (Operations) ACAS (P) Assistant Chief of Air Staff (Policy) 8 A/Cdre Air Commodore ACM Air Chief Marshal AGL Above Ground Level AI Airborne Interception AM Air Marshal AOC Air Officer Commanding AOC-in-C Air Officer Commanding-in-Chief A/P Aiming Point API Air Position Indicator ASI Air Speed Indicator ASL Above Sea Level ASV Air to Surface Vessel AVM Air Vice-Marshal BC Bomber Command BBSU British Bombing Survey Unit BDU Bomber Development Unit CAS Chief of Air Staff C-in-C Commander-in-Chief CoG Centre of Gravity CoP Centre of Pressure c.p.d. Constant Path Difference COS Chiefs of Staff CRT Cathode Ray Tube CSBS Course Setting Bomb Sight D Arm R Director of Armament (Research) 9 DBO Directorate of Bomber Operations D B Ops Director of Bomber Operations D C-in-C Deputy Commander-in-Chief DD B Ops Deputy Directorate of Bomber Operations D O I(O) Director of Intelligence (Operations) D/R Dead Reckoning DRC Distant Reading Compass ETA Estimated Time of Arrival Flg Off Flying Officer Flt Lt Flight Lieutenant Flt Sgt Flight Sergeant Gp Capt Group Captain GPI Ground Position Indicator HC High Capacity HF High Frequency HQ Headquarters HQBC Headquarters Bomber Command I.G. Inspector General IAS Indicated Air Speed I. E. Initial Equipment JIC Joint Intelligence Committee JPS Joint Planning Staff LNSF Light Night Striking Force MAP Ministry of Aircraft Production MC Medium Capacity 10 MEW Ministry of Economic Welfare MPI Mean Point of Impact MTB Main Time Base ORS Operational Research Section ORSBC Operational Research Section Bomber Command OTU Operational Training Unit PFF Pathfinder Force P/O Pilot Officer PPI Plan Position Indicator PRF Pulse Recurrence Frequency RE8 Ministry of Home Security Research and Experiments Department 8 SABS Stabilised Automatic Bomb Sight SASO Senior Air Staff Officer SBA Standard Blind (later Beam) Approach SBC Small Bomb Container SDF Special Duties Flight Sgt Sergeant SHAEF Supreme Headquarters British Expeditionary Force Sqn Ldr Squadron Leader S.S. ‘Skywave’ Signals TAS True Air Speed TBF Time of bomb fall TFF Target Finding Force T.I. Target Indicator 11 TNA The National Archives, Kew ToT Time on Target TRE Telecommunications Research Establishment TV Terminal Velocity U/S Unseviceable VCAS Vice-Chief of Air Staff VHF Very High Frequency Wg Cdr Wing Commander W/T Wireless Telegraphy 12 “The constant struggle at night is to get light onto the target. I foresee a never ending struggle to circumvent the law that we cannot see in the dark” Air Commodore Coningham, 9th December 19391 INTRODUCTION On the night of the 1/2 September 1942, 231 aircraft of Royal Air Force Bomber Command set out to bomb the town of Saarbrücken in south-west Germany.