Allied Air Power Doctrine: Royal Air Force War Manual; Volume I - Chapter 13: Combined Operations

General Considerations

1. In this chapter, combined operations will be considered mainly from the air aspect and attention will be confined to general principles and the difficulties of the problem as they concern the air force. It is, however, impracticable to consider combined operations without realizing the capabilities, limitations and requirements of the three fighting services.

2. " Combined operations " is the term used to de-scribe those forms of operations where naval, military or air forces in any combination are co-operating with each other, working separately under their respective commanders, but with a common aim.

3. Owing to the complex character of modern warfare and to the geographical situation of the British Empire, no large-scale war involving this country can take place which will not call for the co-ordinated efforts of all the fighting services. For example, in the case of military operations overseas, air forces may be required to co-operate with naval forces in the maintenance of sea communications, or in the case of a military landing on hostile territory an air force may be required to assist by establishing temporary air superiority while naval forces provide for the local command of the sea.

4. In any combined operation, the relative importance of the rôles of each service is liable to change during the course of the operation. Therefore, the interests of the service whose share in the enterprise is most vital to its success at the moment, should always be given precedence particularly in administrative matters. Thus, during the period of a landing, military interests predominate and the whole energy of all the services concerned must be devoted to putting the army safely ashore.

5. Before considering in detail any particular form of combined operation, it is necessary to have in mind a general conception of what the sending of an expedition overseas entails, and of the difficulties under which a landing may have to be carried out.

6. A strong expedition involves the despatch of a large number of ships of various types and sizes. To obtain protection these ships proceed in convoy and the speed of the convoy must necessarily be the speed of the slowest ship. Generally speaking, this may be taken as being not more than ten knots.

7. Being in itself essentially a defenceless and vulnerable target, a convoy must, when the menace exists, have protection against sea and air attack. The first is provided by escorting ships of war and the second, in daylight hours, by ships of war, patrolling aircraft, such as large flying boats, and aircraft working from carriers or from a parent ship, according to the opposition likely to be encountered and the type of aircraft available.

8. It is unlikely in any expedition except a dash across a narrow channel that it will be possible to ensure secrecy with regard to the despatch and progress of such a fleet, and it will seldom be possible to deviate from a pre-arranged plan once the expedition has sailed. Accordingly, every arrangement connected with the sailing of the expedition and the landing of the force must be worked out in minute detail and with absolute accuracy, and all orders must be written, before the expedition sails. As a general rule administrative orders only will he issued before sailing ; operations orders being issued under scaled cover and being opened only after the expedition has sailed.

9. Even under the most favourable conditions, the disembarkation of a large number of men and a mass of material is an intricate operation demanding the most thorough organization and the strictest observance of movement orders and time tables. Any occurrence that compels a deviation from the programme will inevitably cause delays and confusion, which in the end may result in upsetting the plan.

10. The landing of an invading expedition, so far from being carried out under most favourable conditions, usually will take place under conditions which are quite unfavourable. Facilities for disembarkation will probably be rudimentary, the beach space on to which the force must land will be constricted, and the vitality and morale of the personnel, if the voyage has been long, will inevitably have been lowered.

11. (i) The necessity for efficient signalling during a combined operation and during the actual landing in particular cannot be too strongly emphasized.

(ii) A combined signal board is responsible for the allocation of responsibility between the services for providing and manning signal communications.

Plans

12. (i) Plans for combined operations fall under two headings :

(a) Those prepared in peace-time as an integral part of a particular war plan or to anticipate a possible requirement in the event of war.

(b) Those formed in war-time to meet a particular situation produced by the course of hostilities.

(ii) Plans prepared under (a) will be influenced considerably by the course of political events, about which the Government will, at its discretion, keep the Admiralty, War Office and Air Ministry informed.

(iii) Plans prepared in peace-time must necessarily he sufficiently fluid to allow of modification to meet unforeseen circumstances, while those produced actually in war will be more definite and detailed in character.

13. When political or strategical considerations indicate the necessity for a combined expedition, the matter is brought to the notice of the Government, which decides whether an expedition is required, and if so, instructs the Chiefs of Staff of the services to furnish their appreciation of the situation.

14. (i) When the Government has finally approved the appreciation and plan submitted by the Chiefs of Staff of the respective services in conjunction with the Board of Trade, the appointment of the commanders and their principal staff officers will be made.

(ii) The respective commanders will then issue preliminary instructions giving a brief outline of the plan and of the general policy as regards organization and administration. These instructions will he followed, as circumstances require, by more detailed instructions, which will be issued in sequence as a separate series.

15. The essence of success in any operation of war is surprise, and the achievement of surprise depends on the degree to which the enemy has been kept in ignorance of the impending operations. The maintenance of secrecy throughout all stages of a combined operation is therefore of the greatest importance. The very nature of the operations and the diversity and extent of the preliminary arrangements and preparatory training make the maintenance of secrecy, without undue curtailment of the necessary distribution of all essential information to those actually concerned, a matter of the greatest difficulty.

Typical Forms of Combined Operation

16. It is impossible accurately to make a complete classification of all the different types of combined operations. The action of air forces will therefore be considered, firstly, in the prevention of a hostile landing and, secondly, in assisting a landing on a hostile shore.

17. In considering any form of combined operation, it must be remembered that though the activity of a navy is restricted by the coast line and the activity of an army is confined to the land, an air force in the air is unaffected by natural obstacles and that once in its element it can operate freely over either sea or land. This freedom of movement depends, however, on the number and disposition of the bases from which the air units can operate ; therefore the aim of every commander of air forces must be to have his aircraft in flying condition at the earliest possible stage in the operations and to have them securely based within flying range of his objectives.

18. (i) The difference between the position of an air force opposing a landing and the position of an air force assisting a landing is that the objectives of the former are few, conspicuous, vulnerable and vital. Crowded into a very small space on a number of ships is a high concentration of the enemy's fighting energy. The ships themselves are distinct targets and so vulnerable to bombing attacks that it is possible for a few well-directed bombs or torpedoes to put out of action a ship and its whole contents, material and personnel.

(ii) The bombing objectives for the invading air force, on the other hand, will usually be dispersed, concealed, not particularly vulnerable to attack, and each by itself will be of comparatively small importance.

(iii) This disparity in the values of their respective objectives will necessitate a far higher degree of efficiency in the invading than in the opposing air force, and will affect not only the form of operation carried out by each air force, but also the composition of the forces involved.

19. An air force co-operating in opposing a landing.—The defence will be in possession of the shore and usually will have at its disposal a number of places suitable for aerodromes and landing grounds. In consequence the defending air force will have a choice as regards the bases from which it will elect to operate.

20. Under certain conditions it may be possible for the defending air force to withdraw to aerodromes beyond the radius of action of hostile bombers and to carry on operations from scattered landing grounds. It will thus be almost immune from attack when at rest : it will possess the power of concentrating or of dispersing, and will therefore be in a position of tactical advantage over hostile air units which will have to operate from a limited number of advanced landing grounds or from carriers.

21. The sequence of duties of the defending air force will be :

(i) to maintain a watch over the enemy's movements.

(ii) to attack the enemy surface forces.

(iii) to gain air superiority in the area of operations during the attempt to carry out a landing ;

22. Reconnaissance.—(i) If the enemy's advanced sea bases are within range of distant reconnaissance aircraft, surveillance of such bases may reveal any activity giving early indication of the assembly of a combined expedition. When such advanced bases are beyond reconnoitring range of shore-based aircraft and should there be no aircraft carriers available to extend the range, the defending force will have to maintain reconnaissance patrols to seaward, extending to such depth as will prevent approaching convoys reaching their anchorages unperceived during the hours of darkness. This depth may be anything up to a distance of 150 miles and will vary according to the speed of approach of the hostile convoys and the hour at which the reconnaissance is being carried out.

23. In addition to watching for the approach of enemy convoys, the air force is responsible for detecting any attempt on the part of the enemy to establish himself ashore on aerodromes or landing grounds from which he can carry out air operations to protect his convoy.

24. Air fighting.—If the enemy has been successful in establishing his air units ashore prior to attempting his main landing, the defending air force should attack these aerodromes, but the aim of the whole of the defence operations should be to prevent the enemy landing, and every effort of the air force must be directed towards the attainment of this aim. The main air operations should be the attack of the enemy troopships and personnel. Only sufficient aircraft should be diverted from this work to ensure such superiority in the air as will enable these attacks to take place.

25. The struggle for air superiority, once the enemy begins his attempt to land, should be carried out by offensive patrols of single-seater fighters working in close co-operation with the bombers, torpedo aircraft and fighters carrying out the main operations.

26. Main objectives.—Troopships are large targets, and are very vulnerable. Moreover comparatively slight damage resulting in a list may seriously affect the disembarkation of troops. Accordingly, when the convoy is approaching its anchorage and comes within bombing or torpedo range of the shore bases, every available aircraft should be used for intensive attacks on the transports. During the actual landing, in addition to the bombing and torpedo attacks against transports, low-flying attacks should be carried out against troops on deck and against small craft carrying troops ashore. In the later stages of a landing when the transports are empty of troops, attacks should be directed against store or supply ships. This is in effect attacking the troops ashore, by striking at their lines of communication. Only exceptional circumstances such as the failure of the defensive line or the very rapid advance of the  invaders would warrant the diversion of aircraft to attack enemy troops who have succeeded in establishing themselves ashore.

27. The probability of a big invading expedition being able to evade discovery by both sea and air reconnaissance during its period of approach is remote, but if a convoy has succeeded in reaching its anchorages unnoticed and discovery has been avoided until after the landing has been commenced the defence even then will generally have facilities for concentrating aircraft at very short notice, from different shore bases, to attack the anchored ships.

28. From the foregoing it is apparent that in air operations the advantage usually lies with the air force opposing the landing. This is due to :

(i) The vulnerability of the attacking convoy, which forms an easy target for the defending air force.

(ii) The difficulty for the attacker of concentrating superior air forces over the area of operations.

29. An air force assisting a landing in the face of opposition by military and air forces.—It will seldom be possible to effect a strategical surprise in making a landing. Such a result could only be obtained if both the intention to despatch an expedition and its actual despatch could be concealed. Modern methods of reconnaissance by sea and air make it probable that the approach of the convoy will be discovered at some time during the hours of daylight once the ships are within a distance of about 150 miles of their intended anchorages. Once discovered, such a convoy becomes a target peculiarly defenceless against attack.

30. Assuming, however, that a convoy evades discovery during its period of approach and begins its landing unopposed during the hours of darkness, it is not to be expected that an expedition of any large size will be able to complete the landing of all the fighting troops with their stores and equipment before daybreak : therefore, at whatever time the landing is commenced, it is inevitable that ships will be found at their anchor-ages at some time during daylight hours, and when this occurs intensive attacks from the air may be expected.

31. The landing of a modern force of all arms on open beaches is a most difficult operation to carry out with precision even under favourable conditions. The troops engaged in it, congregated in small vessels and unable for the time being either to escape or to defend themselves, present a very vulnerable target, and moral and material damage may he inflicted upon them by a determined enemy, sufficient to throw an operation so intricate into disorder and confusion.

32. It follows then, that a landing on a large scale, particularly by day, in the face of a powerful air force, must be protected from enemy air interference. Such protection can best be secured by establishing aerodromes or landing grounds on some other part of the mainland and within effective striking distance of those of the enemy, or by employing during the period of the landing a force of fighter aircraft numerically capable of neutralizing the enemy offensive patrols, while engaging and destroying the bomber formations menacing the landings.

33. The circumstances necessitating the employment of air forces in protecting a landing tend to neutralize the essentially offensive characteristics of aircraft and to make the air force commander use his aircraft defensively. This tendency must be guarded against, for though the role of the air force is essentially protective, this protection must not degenerate into passive defence.

34. The free use of aircraft depends upon the number and disposition of the aerodromes and landing grounds from which they can operate. Therefore, the first requirement of an air force engaged in assisting a landing is secure bases within operating range against the enemy. The acquisition and maintenance of such bases ashore present obvious difficulties, which frequently may be insuperable. The alternative, when this is so, is the use of aircraft carriers.

35. The employment of aircraft carriers as advanced bases in the face of shore-based hostile aircraft is beset with difficulties. First, the carrier itself is very vulnerable to sea and air attack, particularly in regard to the flying decks. Even comparatively slight damage to these may temporarily immobilize all the aircraft on board. Secondly, throughout the whole period of the operations the carriers must maintain steam and be under way to allow the aircraft to fly on and off. The fulfilment of this condition depends upon the fuel capacity of the carrier. Thirdly, the limitations of storage facilities, the dimensions of the lifts, and the restricted space from which the aircraft must operate, limit the size of the aircraft that can be used and the rapidity with which numbers can be put into the air and received back on board. To permit, therefore, of a systematic air offensive being developed against the enemy air forces, either adequate air bases are required ashore or else aircraft carriers must be available to provide sufficient aircraft to engage both the hostile fighters and bombers. Where these conditions cannot be fulfilled, a landing in the face of a watchful and energetic enemy in the air must prove a hazardous operation.

36. Circumstances, however, may occur in which a landing will have to be carried through in the face of an air force which, though undefeated, is both limited in numbers and restricted as regards reserves and general resources. When this is so, the tactical employment of the air units of the force opposing the landing may be restricted by the urgent necessity for conserving strength, in order to exert a maximum effort to oppose the main landing.

37. Any device used by the invaders to compel the enemy to use his aircraft and incur wastage will contribute towards the success of the main operation. Landings either as feints or in order to establish aerodromes or advanced landing grounds ashore may serve to draw air attack and cause the enemy to use his aircraft.

Such preliminary operations however, will eliminate the possibility of achieving surprise for the main landing and before they are undertaken this must be duly considered.

38. Surprise can never he guaranteed, and if a landing is to take place within operating range of the enemy's aircraft there is always the risk that discovery will result in the invading force being exposed to air attack when it is committed to the landing. Generally speaking, therefore, when the scene of the projected landing is within operating range of enemy aircraft, it may be better to precede the main landing by operations to secure local air superiority even at the expense of sacrificing the possibility of strategical surprise.

39. Co-operation during the landing.—In the preceding paragraphs attention has been devoted mainly to the struggle for air superiority which may precede the actual landing of the military force. In the succeeding paragraphs consideration will be given to the operations required after the landing has commenced and the aircraft have become engaged in duties such as reconnaissance, spotting for naval gun fire and observations for army artillery.

40. Reconnaissance.—The requirements and limitations of reconnaissance have been dealt with in Chapter XII, and the general rules and principles laid down there as applying to army co-operation are equally applicable to a combined operation. Reconnaissances during the landing, and in the early stages of the advance on land, should be carried out either by seaplanes, or by fleet spotter-reconnaissance aircraft operating from a carrier. When aerodromes become available, reconnaissance duties should be taken over by the aircraft normally used for military reconnaissances.

41. Spotting for naval guns.—During certain phases of a combined operation, spotting for naval guns engaging land targets will be an air duty of great importance. The landing should be carried out under cover of the ships' guns, and the advance of the troops, until army batteries can be landed and brought into action, will depend on artillery support from the ships. Spotting for ships' guns should be carried out by fleet spotter-reconnaissance aircraft when carrier-borne aircraft are available, or by floatplanes when no carrier accompanies the convoy.

42. Observation for army batteries.—Until the troops, who have landed, have advanced inshore to a sufficient depth to permit of aerodromes being established behind them out of range of enemy shell fire, no army co-operation aircraft will be available to carry out artillery reconnaissance for the army batteries. During this period, the duration of which will depend on the progress of the military advance, observation for the army artillery may have to be carried out by fleet spotter-reconnaissance aircraft or floatplanes according to whether a carrier accompanies the expedition or not.

43. Army co-operation aircraft will be available to carry out their ordinary rôle of co-operation only when it has been possible to erect and establish them on aerodromes ashore.

Anti-Aircraft Defence

44. So long as a convoy is within striking distance of aircraft operating from our own air bases, it may receive a measure of protection from those aircraft, but when a convoy is outside the radius of action of such aircraft it will have to rely for protection upon aircraft operating from carriers and other vessels and anti-aircraft gun fire from ships. Arrangements may also be made for using the Lewis guns of troops on board the transports.

45. Although aircraft constitute the chief defence of the naval and military forces against air attack, no effort must be relaxed to ensure an adequate system of anti-aircraft defence both on the ground and on board ship, and the responsibilities of each of the services in this respect must be clearly defined.

46. The staffs of the three Services will, in collaboration, draw up an anti-aircraft defence plan covering the different phases of the operation. In preparing this plan weight must be given, amongst other considerations, to the possibility of the anchorage being outside the range of army anti-aircraft defences and to the fact that ships providing anti-aircraft fire under certain circumstances have to be withdrawn.

Duties of the Air Force Commander

47. The Air Force commander will command in all respects all R.A.F. units except those of the fleet air arm or attached to the army. He will be responsible for their technical supply and will arrange for supply and administrative services for the R.A.F. units under his command either directly from R.A.F. sources or under arrangements made by one of the other services.

48. Although units of the fleet air arm and air units working under the military commanders will not be under the command of the Air Force commander, he will be responsible for giving advice as to their employment if required to do so. He may also be responsible for the technical supply of such units. The system to be adopted in any particular instance will be decided by the Air Ministry after consultation with the Admiralty or War Office.

49. It is only by complete co-ordination in the employment of air forces that economy and efficiency can be ensured. Such co-ordination can be attained only by close liaison between the staffs of the three commanders.