Archive for the 'Pathfinders' Category

Tactics and the Transportation Plan

On 10 April 1944, 467 Squadron joined a force of 166 aircraft from 5 Group sent to attack the railway marshalling yards in Tours in central France. The Tours trip occupies an interesting period of the bomber offensive when ‘precision’ targets were being attacked more frequently than big cities, so, springboarding off my earlier Tours post, here is an examination of how tactics developed during this time.

Tours and four other marshalling yards attacked that night were included in what was known as the Transportation Plan, part of the preparations for the upcoming invasion of Europe which by this time was less than two months away. The Plan called for the “destruction of thirty-seven railway centres in France, Belgium and western Germany, and especially of the locomotive depots and repair and maintenance facilities in these places, in order to prevent the flow of reinforcements and supplies for the German army in the invasion area.”[1] A key aim was the avoidance wherever possible of French civilian casualties, so accuracy was a priority (indeed, Max Hastings recounts the internal battles between Harris and Churchill on one side and Eisenhower and Tedder on the other about the ability or otherwise of Bomber Command to be accurate enough for the task[2]). The first railway target – Trappes in France – was attacked by 267 Halifaxes and Mosquitos on 6 March 1944 and over the next three weeks, Bomber Command would visit Le Mans, Amiens (twice), Laon, Aulnoye and Courtrai. By 10 May, the Lille raid was by my count the 43rd operation in the series, to a total of 26 distinct railway targets.[3]

For the first month or so of the Transportation Plan, the bombers used Parramatta tactics, very much like those used on German cities, where bombs were aimed at ground markers dropped by Oboe-equipped Mosquitos. The Main Force would attack in one or two waves, usually with a ‘reserve’ period in which the marking would be kept up for any late-running bombers. Crucially, on French targets crews were told not to drop their bombs until the markers went down and if no markers were visible at all, they were to bring their bombs back (as occurred for the second wave on Laon on 23 March). This was clearly an attempt to ensure bombs only fell, wherever possible, on the actual target and not on civilian housing nearby.

Though these attacks were in the main reasonably successful, there were improvements that could be made. Oboe was normally a sufficiently accurate system for city-busting raids but it was fiddly to work with, occasionally failed and was sometimes not accurate enough for precision targets like marshalling yards. If the markers went wide, so did the bombs – a situation seen to varying degrees at Amiens on 15 March, Aulnoye on 25 March, Courtrai on 26 March and Lille on 9 April. In an apparent attempt to reduce French civilian losses (and to avoid wasted effort), on 10 April a Master Bomber was introduced to direct the second attack on Aulnoye. In this case the Mosquitos still dropped their markers by Oboe but instead of then heading for home they stuck around to direct the bombing by radio.

This was, of course, the same night as the Tours operation. Tactics on this raid were somewhat different from the pattern which had become the ‘norm’. Surprisingly, no Mosquitos were sent to Tours and Oboe was not used. The raid was a 5 Group only affair. Lancasters dropped white ‘hooded’ flares to illuminate the ground, and the Master Bomber himself – flying a Lancaster – marked the target visually, by their light. The Main Force attacked in two waves and whilst the first part was highly accurate, the second was hampered by the smoke and flames caused by the earlier raiders and there was subsequently a delay while the Master Bomber re-marked the target.

The Tours trip occurred during a period of clear weather and a three-quarter moon, which meant reasonably bright conditions for bombing and resulted in accurate marking. The vast majority of subsequent railway operations were conducted with another refinement in tactics, which would have helped when the general light levels were not so bright. The pattern was set on 18 April 1944 on a marshalling yard at Juvisy, near Paris.

Oboe Mosquitos would first drop their ground markers, followed immediately by illuminating flares by Lancasters in the Newhaven style. The Master Bomber would assess the fall of the target indicators by the light of the flares, determine the required correction or even drop his own markers and instruct the Main Force to attack accordingly. The results, when everything went to plan, were immediate and effective. Juvisy suffered “immense” damage. On the same night, Rouen got “exceptionally severe” effects from a “magnificent” concentration of bombing.

The problem, however, was when things went wrong. At Tergnier, also on 18 April, the Oboe Mosquitos failed and the visual markers fell wide. So did the bombing. Communications between the Master Bomber and the Main Force were absolutely critical. It was an unwieldy system because if the Master Bomber was in a Mosquito he could not talk directly to the Main Force. The VHF radios in the Mosquitos were in relative short supply, so a ‘Controller,’ whose Lancaster had been fitted with one of the VHF radios, was required to relay instructions to the rest of the Main Force over standard radio and wireless telegraphy. When communications failed, so, on many occasions, did the bombing, such as what happened to the second wave at Villeneuve-St-George on 26 April and Malines on 1 May. But when everything worked it proved most effective in highlighting which target indicators the crews should aim at. On 6 May, for example, 143 aircraft attacked the marshalling yards at Mantes-Gassicourt. The first Oboe marking failed so the illuminating flares dropped first, followed by three loads of target indicators which were scattered wide of the aiming point. Crews were ordered to bomb in between all sets of markers, until a salvo of reds landed bang on the aiming point. The Master Bomber was able to adjust and instruct crews to aim at the new, accurate, markers, until more reds fell off the target. The resulting confusion was resolved when a set of white markers was dropped accurately, but by now smoke and fire obscured all the indicators, so the Master Bomber ordered crews to simply aim at the fires. Had the Master Bomber not been there, or had the radio been jammed or otherwise unavailable, the raid would certainly have been far more scattered than it was.

The other issue with direct marking of the aiming point happened when the bombing was, well, too good and the markers were obscured by smoke. This, of course, is what happened following the first wave of the attack on Tours, and it happened again at La Chappelle on 20 April. On this occasion the aiming point requiring remarking slightly away from the original target indicators.

Yet another development in target marking was devised to counter this. It was first deployed in an attack against an airfield at Lanveoc-Poulmic, near Brest, on 8 May.[4] Here the markers were deliberately dropped upwind of the actual aiming point. The Master Bomber would determine how far away and in what direction from the aiming point the markers had fallen and then calculate a ‘false bombing wind’ which could be fed into bombsights. The theory was that, if the sight was aimed at the marker, the adjusted wind setting would ensure that the bombs themselves landed on the real aiming point. It was a good theory and the resulting bombing was highly accurate. The only problem was that it took time for the markers to be dropped and assessed and for the false bombing wind to be calculated. The Main Force was timed to arrive having allowed sufficient time for the process to be completed but it needed good communications and good timing from all crews to be practical.

The next night the new system was used again. The date was 10 May 1944, and the target was Lille. Like the Tours trip, this used slightly different tactics to others in use at the time. While the three other railway raids carried out on the same night (to Courtrai, Ghent and Lens) all used Oboe Mosquitos, the target at Lille was marked visually under the light of illuminating flares – a classic Newhaven attack. Unfortunately what happened was exactly what offset marking was intended to avoid, when the first markers were extinguished by the early bombing, perhaps because crews were not yet used to the new tactics and simply forgot to apply the correction. After a short period the master bomber called a halt to proceedings so that new markers could be dropped, but it appears the resulting delay of some 20 minutes allowed the defences to get their act together, and they extracted a heavy price. Twelve out of 89 aircraft failed to return, among them B for Baker.

© 2013 Adam Purcell


[1] Lawrence 1951, No. 5 Bomber Group, R.A.F. 1939-1945, Faber and Faber Limited, 24 Russell Square, London W.C.1, p.164

[2] Hastings, Max 1979. Bomber Command. Michael Joseph Ltd London, p.327

[3] Stats extracted from Night Raid Reports Nos. 545-600. This tally does not include a raid to Aachen (11APR44) as this target was in Germany

[4] ‘Offset Marking’ and the Lanveoc-Poulmic raid are described in Lawrence 1951, p.183-5

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A Pathfinder Glossary

The Pathfinders of Bomber Command used a variety of techniques and tactics when marking targets for the Main Force. These were all referred to by codewords. Here is an alphabetical glossary of some of the many Pathfinder terms I’ve come across in the course of my research:

  • Backers-Up: Pathfinder crews scattered through the Main Force who dropped secondary target indicators (usually green) visually on the red primary target indicators. This was aimed at ensuring that the target remained marked for the entire attack, even after the primary markers had burnt themselves out.
  • Blind Marking: Aiming bombs or target markers by means other than visually – usually referring to the use of an electronic aid like H2S, Oboe or Gee.
  • Blind Marker-Illuminators: First Pathfinder aircraft on the scene during a NEWHAVEN attack who used H2S to drop illuminating flares and target indicators (usually green or yellow). The light provided by the flares could then be used by the Visual Markers.
  • Controller: Officer who is in R/T contact with the Pathfinder Markers and Illuminators, and W/T contact with the rest of the Main Force. The Controller decides which markers are accurate and instructs the Main Force crews accordingly.
  • Emergency Parramatta: Used where the Visual Markers could not see the aiming point due to cloud or haze. They would hold on to their markers and the Backers-Up would instead aim their secondary target indicators on the markers dropped by the Blind Marker-Illuminators.
  • Emergency Wanganui: Pathfinder aircraft carried a single WANGANUI flare for use where unexpected heavy cloud precluded the use of ground markers.
  • H2S: Airborne ground-mapping radar carried by bombers. Could distinguish built-up areas and most effective where a clearly-defined feature – such as a coastline – existed.
  • Illumination: Dropping of parachute flares to light up the target area, enabling the aiming point to be identified visually by Pathfinders or by the Main Force. Carried out by the Flare Force.
  • Main Force: ‘Ordinary’ rank-and-file Bomber Command crews.
  • Markers: Generic term for Target Indicators or Wanganui makers. Confusingly, could also refer to the crews actually doing the marking.
  • MUSICAL: Prefix codeword for raids marked by crews (usually in Mosquitos) using OBOE. Distributing marking Mosquitos throughout the bomber stream aimed to ensure that the target was always marked by primaries. Eg MUSICAL NEWHAVEN, MUSICAL PARRAMATTA or MUSICAL WANGANUI.
  • MPI: Mean Point of Impact. The estimated ‘centre’ of a cluster or target indicators, sky markers or bombs.
  • NEWHAVEN: A method of ground-marking whereby the target was first located by Blind Marker-Illuminators, then backed up by Visual Markers dropping Target Indicators. Since the markers were aimed visually this could only be used with clear weather prevailing over the target. If a Newhaven attack was impossible an Emergency Parramatta would be used instead.
  • OBOE: Navigation/blind-bombing aid using beams from two base stations in England. Extremely accurate but could be used by only a small number of aircraft at a time, so was used primarily to drop target markers.
  • PARRAMATTA: Classic area bombing technique where the primary markers (red or yellow) were dropped on the target by H2S-equipped Blind Markers. Backers-Up would then aim their (usually green) Target Indicators at the MPI of those primary markers for the benefit of the Main Force.
  • Primary Markers: Target Indicators or flares aimed at the Aiming Point itself. As opposed to Secondary Markers.
  • Release-point flares: Parachute flares, usually red with green stars or green with red stars, used in WANGANUI attacks. Also called skymarkers.
  • Secondary markers: Target Indicators or flares aimed at Primary markers. Dropped by Backers-Up to keep the target marked before the primaries burned out.
  • SUPPORTERS: Experienced Main Force crews briefed to go over the target and bomb at the same time as the leading Pathfinders, to ‘swamp’ the defences and make it difficult for radar-predicted flak to lock onto one individual aircraft.
  • Target Indicators: Ground markers consisting of a small bomb case which was set to burst at a certain height above the ground (3,000, 6,000 or 10,000ft), scattering up to 60 small ‘candles.’ The candles then ignited and cascaded slowly to the ground. Once on the ground they continued burning with a distinctive colour – red, green or yellow. Most burned for about three minutes but some burned, less brilliantly, for up to seven. Called ‘Christmas trees’ by the Germans.
  • Visual Markers: Pathfinder crews that identified the aiming point visually, and dropped their own markers (usually red) on it. Usually the most experienced crews in the Pathfinders.
  • WANGANUI: Blind bombing skymarking technique used when aiming point is covered in cloud. H2S-equipped aircraft dropped parachute flares and the Main Force aimed at the flares themselves (or the MPI of the flares if they were being scattered by the wind), bombing on a pre-arranged heading. Not terribly accurate and very susceptible to the wind. Flares used could variously be referred to as ‘skymarkers’, ‘release point flares’ or, simply, ‘Wanganuis’.

© 2013 Adam Purcell

Sources:

NAA: A11343, 77/AIR. [No 467 Squadron] Pathfinder Force – Technique. Barcode 304281

Middlebrook, Martin (1973). The Nuremburg Raid