Blue-on-Blue: Bomber Command and Operation Tractable, 14 August 1944

Examined at the tactical level, the Normandy campaign sometimes appears as one long sequence of blue-on-blue or 'friendly fire' episodes. However, hardly any were actually caught on camera. One of the few that were involved RAF Bomber Command and First (Canadian) Army during Operation Tractable on 14 August 1944. This blog draws heavily on unpublished research by Group Captain Steve Lloyd RAF (Rtd), formerly of the Air Historical Branch.

From July 1944 onwards, all the major set-piece Allied ground offensives in Normandy were preceded by heavy bombing operations against the German lines undertaken by the strategic bomber forces – Bomber Command and the US Eighth Air Force. Both forces were assigned at virtually no notice to a ground support task that differed fundamentally from their normal strategic role. The importance that Allied ground commanders attached to these operations may be measured from their repeated requests for heavy bomber support, which continued throughout July and into August, September and October.

Nevertheless, from a tactical perspective, this approach to offensive warfare raised a number of acute difficulties. Originally, Allied commanders intended the heavy bombers to bomb gaps in the German lines. However, while they certainly inflicted significant losses on German ground forces in Normandy, it was soon established that their primary effects were not so much physical as psychological – the shock and disorientation inflicted on the defenders. Yet these effects were temporary. They had to be exploited quickly by Allied troops on the ground, who had therefore to be deployed well forward when the bombers attacked. This inevitably increased the danger that they themselves might fall victim to any bombs dropped off-target, or to the tendency for bomb patterns to ‘creep back’ from their target areas.

A variation on the use of heavy bombers to bomb through the German lines involved using them to protect the flanks of advancing Allied forces. This could be achieved through the direct targeting of threatening German units or through extensive cratering to make ground impassable, or through a combination of both methods. Nevertheless, even then, quite close proximity between the bombed areas and Allied ground forces was an unavoidable feature of such operations.

Protecting the flanks: the results of Bomber Command 
bombing at Sannerville during Operation Goodwood, 
18 July 1944

Complicating matters further was an absence of formal command and control machinery for the use of heavy bombers in a ground support role. The formal command structures through which the Allied armies dealt with their tactical air forces were entirely absent, and planning was conducted on an ad hoc basis. It was not especially difficult for Allied air commanders to understand the essentials of British and American ground plans in Normandy, but their Army counterparts, for reasons that are entirely understandable, had virtually no grasp of the capabilities, limitations, tactics, techniques and procedures of the strategic bomber forces.

On 13 August 1944, with German forces resisting stubbornly on the road from Caen to Falaise, 21st Army Group decided to launch an attack from the north-east across the River Laison - Operation Tractable. An infantry and an armoured division from First Canadian Army were to advance from the area Soignelles-Estrees-La-Compagne. The object was to seize the high open ground southeast of the River Laison. After this had been accomplished, they were to continue the advance and capture the ridge dominating Falaise as a prelude to the capture of the town and the closure of the so-called ‘gap’ between Falaise and Argentan, cutting off German forces to the west.

Intelligence suggested that a powerful German armoured group was positioned in the area of Soumont-Le-Quentin, quite close to the Falaise road. First Canadian Army therefore requested that Bomber Command bomb this area after the ground assault had been launched, so as to prevent a German counter-attack on the Canadian right flank. The request was first submitted on 12 August in the expectation that the attack would commence the following day. However, Tractable was then postponed by 24 hours, and further discussions took place on the afternoon of the 13th on the employment of heavy bombers. Six aiming points were selected at Quesnay, Aisy, Soumont St Quentin, Bons Tassilly, Fontaine-Le-Pin and an area north of Hamel-Le-Marais. Heavy bombers were to start bombing the area two hours after the launch of the ground assault.

The Operation Tractable plan, involving a ground advance to the
east while heavy bombing protected First Canadian Army to
the west

This meant that the main target areas were on approximately the same latitude as the advancing Canadian forces, albeit further to the west. Moreover, to reach their aiming points, the bombers would have to fly over extensive rear logistical and assembly areas positioned to sustain the ground offensive.

Second Tactical Air Force was also to provide air support. Thirty minutes before H-Hour, medium bombers of 2 Group were to attack three defended localities in the thickly wooded valley of the Laison. At the same time, fighter-bombers of 83 and 84 Group would attack strong points and gun positions on the high ground between Olendon and Sassy, south-east of the Laison.

On 14 August, visibility was very good, but there was a slight wind blowing from the north. The Canadians moved forward from their start line at 1200 hours and made satisfactory progress. Bomber Command dispatched 811 aircraft, which began to arrive over the area at 1400 hours. The aim points were correctly marked and heavy concentrations of bombs fell on all six, a total of 3,723 tons being dropped by all the aircraft. Air photographs taken shortly afterwards confirmed the accuracy of the majority of the bombers, but the attack was called off at 1530 – half an hour early – after a number of aircraft dropped their bombs between four and six miles north of the target area. In total, 77 bombers were involved, 44 of which ironically belonged to 6 (Royal Canadian Air Force) Group. A total of 112 troops were killed while 142 were posted missing, and 376 were wounded; 265 vehicles, 30 artillery guns and two tanks were destroyed.

Bomber Command aircraft bombing Quesnay
during Operation Tractable

A field at Quesnay that still bears the scars

The best-known photograph of the blue-on-blue incident;
Allied troops on the Caen-Falaise road look on in horror 
as bombs fall behind them near the Haut Mesnil quarry

The Air Officer Commander-in-Chief, Bomber Command, Air Chief Marshal Sir Arthur Harris, subsequently ordered an enquiry and produced a report on the incident. In it, he addressed the key issues under three basic headings that might be described as strategic, operational and tactical. The fundamental strategic issue was that Bomber Command was a strategic bomber force and was trained as such – typically for night operations against urban and industrial targets in Germany that could hardly have been more different from the tactical support operations they found themselves conducting in Normandy. The Command was therefore trained primarily to operate in darkness, and it was not trained to fly in formation. In the dark, aircraft operated individually according to an overall plan, navigating by prescribed routes to the neighbourhood of their objective and bombing under conditions in which no details of the ground could generally be seen. Bombing was guided by pyrotechnic markers of varying types placed on or near the objective by Pathfinder aircraft. Subsequent corrections were made on the instructions of so-called Master Bombers.

Neither the pilot nor the navigator had much view of the ground. The air bomber alone could direct the aircraft  by means of map reading with reference to the ground beneath, but his training in this field was limited, mainly because the metier of the force was night bombing. Locating the aircraft’s position by map-reading from objects on the ground was normally impossible in darkness.

Air Chief Marshal Sir Arthur Harris, AOC-in C 
Bomber Command

As the task of supporting ground troops had only very recently been assigned to Bomber Command, it was not, of course, realistic to overhaul their entire training regime, and it would have made no sense to do so, in any case, given that they were still primarily intended to conduct the strategic night bombing role. As Harris put it,

This training and the organisation which produces it cannot be changed at a moment’s notice, or indeed at many months’ notice, to enable the force to operate with 100% efficiency in so entirely different a role as close direct support to troops on the ground in daylight … With these facts in view, when urgent demands began to arrive from the army for assistance by the heavy bomber force, it was invariably pointed out that we would do our best within the limits of our experience and training to meet their requirements, but that grave risk inevitably existed in these circumstances of some bombing going astray and taking effect upon our own troops. Nevertheless … the Army authorities concerned expressed ready acceptance of the risk in exchange for the approved decisive effects of such bombing in forwarding their military plans.

Under the operational heading, Harris pointed out that consideration of the Operation Tractable plan had only started on 12 August. This reflected the fact that the broader Allied plan for cutting off the German retreat from Normandy by closing the gap between Falaise and Argentan was only agreed on the 9th. Tractable was very much a last-minute venture devised in great haste. Bomber Command considered attacking the target areas by approaching them from the west. However, this would have required a routing directly above the German lines, during which time their aircraft would have been exposed to heavy anti-aircraft fire. Quite apart from the risks involved, only a few days before, during Operation Totalize, heavy bombers of the Eighth Air Force routing towards the battle area from this direction had been scattered by German flak, and some had mistakenly bombed Allied ground forces as a result. Fearing that something similar might happen in Tractable, Harris insisted that his aircraft should fly north to south instead.

Originally, Bomber Command argued that they should strike the target areas starting with those furthest south and progressing to the more northerly locations. This was due to the forecast northerly wind direction. Harris was concerned that, if his aircraft bombed north to south, many of the more southerly aiming points and target markers would be obscured by smoke and dust during the later stages of the operation. However, First Canadian Army contended that the targets should be attacked from north to south to conform with their projected advance. Understanding their perspective, Harris agreed. The risk that the markers might be obscured was, in his words, ‘accepted at the particular insistence of the Army’. He felt the risk was justified given the potentially decisive role of the heavy bombers.

The most chilling of the surviving photos; the location
 is St Aignan, although the photo is labelled
'Falaise area'

At higher magnification, numerous Allied vehicles can
be seen; no such clarity would have been available to
the air bombers thousands of feet from the ground

Finally, at the tactical level, Harris’s investigation soon identified a familiar pattern. The bombing errors started when a Pathfinder aircraft and 13 bombers of 4 Group and 6 Group bombed an area around St Aignan. At the time, the Master Bombers, who were over the correct target area further south, instructed all crews to bomb on the yellow target indicators. Several of the crews who bombed St Aignan reported seeing yellow target markers in this area. Another 12 aircraft then released their bombs in the same vicinity after a Pathfinder incorrectly marked the target, having again seen yellow lights on the ground.

Harris then described how another 23 aircraft from 6 Group bombed the quarry at Haut Mesnil in error.

This was started by two aircraft of No 428 (RCAF) Squadron who bombed almost simultaneously. They had been briefed to expect to see smoke arising from aiming point 21, which should have been bombed by another force before their arrival. They appear to have mistaken the smoke rising from the erroneous bombing near St Aignan for the smoke from aiming point 21. The Master Bomber concerned, who was operating on and viewing the correct target, instructed arriving aircraft to ‘bomb yellow target indicators. You will find them when you have passed the first column of smoke.’ This appeared to fit the picture as these aircraft saw it and they also claimed to have seen yellow target indicators burning in the neighbourhood of their proposed target.

Next, an aircraft from 460 (RAAF) Squadron struck the same area, after the air bomber saw what he thought were red target indicators burning on the ground, ‘which he had previously seen cascading’, i.e., falling through the air. Another aircraft from 460 squadron then bombed what he thought were yellow target markers. This was enough to draw in a further 24 bombers from 1 Group, which all released their loads in the vicinity of the Haut Mesnil quarry.

An extraordinary photograph that captures the bombing
near the Haut Mesnil quarry

At very high magnification, it is possible to see the white Allied 
recognition stars on the vehicles; again it should be stressed that
the air bombers would have had no comparably detailed view 
of the ground

All the mistakes could have been avoided if the air crews involved had correctly estimated the interval of time between crossing the French coast and arriving over the target area, and they were under clear instructions to do so. However, this technique inevitably involved an element of approximation in itself. When their knowledge of the elapsed time was contradicted by a visual picture in which the location of the target areas was ostensibly confirmed by target markers, smoke and the sight of other aircraft bombing, and by the instructions of the Master Bombers, they chose to accept what appeared to be the evidence of their eyes and ears. At the same time, due to the direction of the wind, they were unable to see the target markers released further south over the correct areas. In Harris’s view, the aircrew ‘too light-heartedly abandoned’ their timed approaches from the coast. The perspective of the crews would doubtless have been very different, but several were afterwards disciplined, and revised instructions were issued for operations by Bomber Command in support of the Army.

Clearly, the appearance of target markers in the wrong locations played a key role in the Tractable blue-on-blue incident. After it was firmly established that the indicators could not have been dropped by Bomber Command Pathfinders, Harris sent an officer – Group Captain SC Elworthy (later to be Chief of Air Staff and, subsequently, Chief of Defence Staff) – to France to investigate. He duly reported to Headquarters, 84 Group (which was co-located with Headquarters First Canadian Army) on 20 August. There, he saw the Senior Air Staff Officer (SASO) and the Group Captain Operations and explained the sequence of events as they were so far understood. In particular, he raised the question of the yellow lights, which had allegedly been seen on the ground around St Aignan and the Haut Mesnil quarry. He was ‘immediately told that yellow smoke, flares and celanese strips were the standard signals for troops of all allied armies in France to indicate their positions to our own aircraft’. He was shown a copy of the First Canadian Army Operations Standing Orders confirming that this was so. Elworthy’s subsequent record deserves to be quoted verbatim.

I pointed out that crews claimed to have seen yellow lights looking like target markers before any bombs fell in the areas occupied by our own troops, and asked, therefore, whether these yellow flares and smoke would only be fired by troops after they had actually been attacked by friendly aircraft. I was informed that, owing to there having been numerous minor incidents involving the attack of friendly troops by our own tactical aircraft, it was quite common for these signals to be displayed if the troops imagined they were going to be attacked ... I could get no direct evidence that yellow flares were alight on the ground prior to the first bomb falling behind our lines, but it would appear most probable that they were. The manner in which these yellow flares, smoke and strips are laid in such circumstances is in the form of a cluster, and thus they resemble the pattern of target indicators on the ground.

No information had previously been given to Bomber Command that this system of ground-to-air recognition was in use. Even more remarkably, Harris’s SASO, who had hurriedly arranged the operation with First Canadian Army in France on the 13th, had specifically asked if any confusing pyrotechnics might be employed by the ground troops, and had been assured that they would not.

Bombs falling near St Aignan on 14 August 1944; the
Army's yellow recognition flares are clearly visible.
Curiously, this photo was incorrectly labelled as
Bons Tassilly

Again, at very high magnification, it is possible to see
Allied vehicles in the photograph

The appearance of the yellow flares was thus explained. However, at least one of the crews reported seeing red target markers too, both in the air and on the ground. Where could these have come from?

Shortly after Operation Tractable, a sensational story appeared in the press, written by war correspondents in Normandy. It described how a wholesale disaster had had only narrowly been averted during the operation following the intervention of several of the Army’s Auster observation aircraft, which flew across the areas being bombed in error, firing red Verey lights. The story suggested that this courageous action prevented the entire bomber force from committing the same mistake. Harris perfectly summed up the reality:

My comment on this is that in the first place the rest of the bombing was under way, firmly controlled by the Master Bombers and achieving excellent results on the correct aiming points. In the second place, red Verey lights fired into smoke or seen through smoke burning on the ground are likely to and did, in fact, give a misleading imitation of target indicators. However well intentioned, therefore, these Auster aircraft succeeded only in making confusion worse confounded.

Two very obvious points emerge from the story of the Operation Tractable blue-on-blue incident. First, when operations are planned at the eleventh hour, there is an increased risk of planning blunders or mistaken actions at the tactical level, which, among other things, may jeopardise clear combat identification. Second, particular care is needed when joint operations are mounted that involve ground and air forces unfamiliar with one another and unused to collaboration.

The precise impact of the Operation Tractable blue-on-blue incident is difficult to gauge. The Allies had hoped that Falaise would be captured on 14 August, but Canadian troops did not enter the town until the 16th. This was largely because of German resistance north of the town and was not a direct result of the fact that St Aignan and Haut Mesnil were bombed in error by Bomber Command. Nevertheless, it is most unlikely that the blue-on-blue exerted no influence at all on the progress of the Canadian offensive and, to that extent, it must be seen as one contributory factor in the Allies’ failure to close the Falaise-Argentan gap before many thousands of German troops escaped through it.

First (Canadian) Army's advance towards Falaise, showing the
intended bombing areas for Operation Totalize and Tractable

The area of the Operation Tractable blue-on-blue