Jonathan Bailey wrote that the First World War was the time of a true revolution in military affairs about the development of artillery firing. One of the first significant developments that took place was the creation and refinement of the ‘clock code’ system. Using this system, a pilot of the Royal Flying Corps, the forerunner to the Royal Air Force (RAF), was able to correct the fall of shot of the artillery by passing to the artillery battery commander details of how far from the target the guns were. The pilot would correct the shooting of the artillery by pointing out how far away and in what direction the shells of the guns had landed. The distance would be passed on using numbers and the direction using the picture of a clock face. The target was placed in the middle of the clock face and shells that fell beyond the target and on a straight line to the target would be corrected with a call of twelve, if it fell short on the same line the call would be six, at ninety degrees left of the target nine and ninety degrees right three. Any other direction would be corrected by using the hour on the clock with which it corresponded. This system would prove to function perfectly well throughout the whole of the First World War and was the system with which the RAF went to war in 1939.
The system of correcting artillery fire remained unchanged until 1938. The Air Council were against making alterations to the clock code system as they felt that it was adequate to meet the needs that the army would face in future conflicts. They felt that light aircraft could not be kept in action close to artillery units, as had been the case in the First World War. The Air Council were also fearful of introducing a new, untried, and unfamiliar system with the growing tensions in Europe at this time. The War Office was unimpressed with the Air Councils attitude and pushed for more to be done. The Air Ministry agreed to trials between the Air Officer Commanding No. 22 (Army Co-operation) Group and the Commandant of the School of Artillery in December 1938. The results of these trials and further trials conducted to test aircraft as well as procedure. The results were that light aircraft over the battlefield could observe fire with the ‘clock code’ system. Spitfires conducted mock attacks on the aircraft and the Taylorcraft light aircraft observing the artillery fire had a good chance of dodging the fire of a modern fighter. There was, however, no training for pilots in registering targets for the artillery. If an artillery officer required an appraisal of a prospective target, the request would have to be sent along the command chain via an air liaison officer. When the artillery battery received the information, it was usually out of date. There was also pressure from within the War Office to establish a Flying Observation Post (Flying OP) and to begin plans to train Gunner Officers to fly. A Flying OP was to work in conjunction with Ground Observation Post (Ground OP) in establishing targets to be engaged and operating deep behind their lines to be afforded the protection of friendly anti-aircraft guns.
The first of these Flying OPs was established in February 1940. This force was established to:
[d]etermine in the light of practical experience obtained under war conditions the possibilities and limitations of the Flying OP, the most suitable type of aircraft and the most suitable organization [sic].
The tests were to be conducted in three parts. The first was an initial training period. The second a practical training with the French, and a final test in the French Army area in conditions of actual warfare including shoots against German targets it was at this time that the term Air Observation Post (Air OP) was adopted. The flight was sent to France on 19 April 1940. The first of the three tests were conducted after the flight had moved to the continent. The final of the three tests was due to be carried out in early May, and the forces were established ready to conduct the tests on 9 May 1940. The following day the Germans began to implement Fall Gelb (Case Yellow): the invasion of France and the Low Countries. The artillery designated for the tests were forced to move back to their formations leaving the Air OP Flight (D Flight) waiting for the campaign to stabilise when it was clear that this would not happen D Flight was recalled to England.
One of the first official moves at changing artillery co-operation policy was a letter regarding the subject sent from the Director of Military Co-operation Air Commodore Victor Goddard to Barratt at Army Co-operation Command. In this letter, Goddard states that the Air Staff were against the formation of:
[s]pecial air units for artillery observation or reconnaissance, unless it can be clearly shown that there is an urgent requirement for such units which cannot be met by Army Co-operations squadrons.
The School of Artillery recommended that a certain number of aircraft should specialise in artillery work and should be trained by the School of Artillery so that they had the same tactical knowledge and the same the understanding of gunnery as an artillery officer. This was just one aspect of an idea by the School of Artillery to allow aircraft to have tactical control over the fire of artillery batteries. To facilitate this, the school further recommended that a multi-seater aircraft should be employed in this work to allow an artillery officer to conduct the shoot according to artillery methods without the need for the artillery officer learning to fly. Artillery officers were also to be seconded to army co-operation squadrons specifically for artillery work. The co-operation between the School of Artillery and Army Co-operation Command is evident and is surprising given the general relations that existed between the army and RAF in the wake of the Battle of France and the fall out that it had caused between the two services.
Barratt, in a letter to the Under-Secretary of State for Air, wrote that:
I consider that in order to get a true and undistorted picture of this problem, it is first desirable to set out the problem as the Army [sic] sees it, and to show in this picture what they conceive to be their requirements.
Again the desire to see the problem from a view that would almost certainly be contradictory to the RAF shows that Barratt and his command were willing to adopt a different approach and attitude in co-operating with at least one part of the army. Barratt also voiced his concerns regarding the ability of the Air OP to operate in the face of enemy action. It was felt that ‘the Air OP must be entirely vulnerable to any enemy fighters which cares to shoot it down’. Barratt’s concern over the safety of his pilots who may be conducting shoots using the Air OP system was to be a recurring issue in the development of artillery reconnaissance.
Barratt’s response to the trials was one of scepticism, and he considered ‘that body of experience gained in the late war and since has all pointed to the advantages of the ‘Clock Code’ system’. Barratt’s belief in the ‘clock code’ system stemmed more from the fear of false conclusions being drawn from brief experiments than from any sense of conservatism about changing the system used for artillery reconnaissance. This became a realisation when Barratt was forced to explain to the Under Secretary of State for Air about the lack of efficiency regarding artillery co-operation in Army Co-operation Squadrons. Barratt wrote that:
I feel that much of the falling off in efficiency in this part of the Army Co-operation Squadron task has been due to the propagation of rumour as to other and better methods than those shown in AP 1176.
Further trials were conducted using the artillery method during April 1941, and the conclusions reached were similar to those seen previously. These were that the artillery methods of ranging by corrections to line and range are simpler, quicker, and more efficient than any method based on the ‘clock code’.
The failures of the ‘clock code’ system in France combined with further problems faced in the fighting in Libya led to a loss of confidence in the system in the army. Barratt responded that the ‘clock code’ system was not at fault in these operations but that the aircraft employed in it were operating in the face of intense enemy opposition. He was concerned that the trials had been too few and were skewed in favour of a positive result by the School of Artillery. While these concerns may be interpreted as merely blocking a new development that had been shown to work to preserve the autonomy of the RAF while conducting army co-operation work. The evidence of co-operation between Army Co-operation Command and the School of Artillery, shown above, leads more to the conclusion that Barratt felt that the procedure could not be successfully carried out, and wished to see more trials conducted before it would receive his approval.
The procedure for artillery reconnaissance first developed during the First World War was only suitable for the conditions of that war. The lack of fluidity and almost stable front lines allowed a system to develop, quickly, this system, however, was only suited to those conditions. This was very quickly discovered during the first major test of this procedure against the quicker and more mobile warfare of the German Wehrmacht in 1940. The attitudes of both the British Army and the RAF to co-operation during the inter-war period, in Britain at least, did little to improve the situation before the British Expeditionary Force was stationed in France. This left those charged with the responsibility of modifying the existing procedure with only the experience of the First World War to guide them and on which to base their expectations. Much co-operation between the School of Artillery and Nos. 70 and 71 Groups of Army Co-operation Command occurred, despite the general feeling of animosity still felt by both services in Britain. This co-operation was the most that had been seen between the army and RAF since the formation of the RAF as an independent force in 1918. Barratt’s move to block the adoption of the new procedure that was being trialled during 1941 can be interpreted in several ways. His reasoning for doing so, however, appears to be that of confirming the results already achieved through more rigorous and testing trials to confirm the results. Through further testing at a higher level the procedure, as well as those responsible for carrying it out, would be exposed to more stress and so a greater degree of authenticity could be achieved. Trials of this nature would also confirm if the procedure could be implemented with ease by the majority of pilots whose responsibility would be increased from observing the fall of shot to conducting shoots, potentially in the face of enemy opposition. Barratt’s major concern with the new system appears to be its increased complexity, and he was rightly concerned after his experiences in France that pilots would be unable to conduct the shoot if they had to keep a lookout for enemy fighter activity continually.
Header Image: An Auster Mark IV of an Air Observation Post squadron undergoes servicing at its base after being damaged by anti-aircraft fire while flying over the 8th Army Front in northern Italy. (Source: © IWM (CNA 3341))
 A longer version of this article can be found in Canadian Military History, 23:1 (2014), pp. 71-88.
 Jonathan Bailey, ‘Deep Battle 1914-1941: The Birth of the Modern Style of War,’ Field Artillery Journal, (1998), pp. 21-7.
 Ralph Barker, A Brief History of the Royal Flying Corps in World War I (London: Constable & Co., 2002), p. 63.
 H.J. Parham and E.M.G. Belfield, Unarmed into Battle: The Story of the Air Observation Post, Second Edition (Chippenham: Picton Publishing, 1986), p.14.
 Darrell Knight, Artillery Flyers at War: A History of the 664, 665, and 666 ‘Air Observation Post’ Squadrons of the Royal Canadian Air Force (Bennington, VT: Merriam Press, 2010), p. 27.
 Parham and Belfield, Unarmed into Battle, p.15.
 Ibid., p.16.
 Karl-Heinz Freiser, The Blitzkrieg Legend: The 1940 Campaign in the West (Annapolis, MD: Naval Institute Press, 2005), p. 79.
 Parham and Belfield, Unarmed into Battle, 16.
 The National Archives (TNA), AIR 39/47, Letter from Air Commodore Goddard, Director of Military Co-operation to Barratt regarding Artillery Co-operation Policy, 8 December 1940.
 For more information on the army’s reaction to the Battle of France, see: TNA, CAB 106/220, Bartholomew Committee Final Report.
 TNA, AIR 39/47, Letter from Barratt to Under-Secretary of State for Air regarding co-operation with the Royal Artillery, 29 January 1941.
 Ibid., Appendix A, 29 January 1941.
 Ibid., Letter from Headquarters Army Co-operation Command to Headquarters No. 70 Group, Artillery Reconnaissance Trials, 12 April 1941.
 Ibid., Letter from Barratt to Under Secretary of State for Air, 14 April 1941.
 Ibid., Letter from CGS on Artillery Reconnaissance, 5 May 1941.
 Ibid., Letter from Barratt to Major-General Otto Lund, GHQ Home Forces, in response from letter from CGS on Artillery Reconnaissance, 10 May 1941.
 For example, see: David Ian Hall, Strategy for Victory: The Development of British Tactical Air Power, 1919-1943 (Westport, CT: Praeger, 2008), pp. 89-103.