Allied Air Power Doctrine: Royal Air Force War Manual; Volume I - Chapter 8: Air Bombardment

The Aim

1. The principal aim of bomber aircraft in all air bombardment operations is to deliver the bomb at the decisive point in the most effective manner possible and, while aircraft must be prepared to fight in order to achieve this aim, lighting must be regarded only as a means to this end.

2. To accomplish this aim, the whole striking force, or as great a proportion of it as is practicable, should consist of bomber aircraft carrying a full load of bombs and, so far as possible, all resources available for offensive action should be devoted to the delivery of the most continuous and effective air bombardment and not (as explained in Chapter VII) diverted to the provision of fighters or lightly loaded bomber aircraft to accompany and support them.

The Selection of Objectives

3. (i) The selection of objectives for air bombardment will depend upon :

(a) The nature of the war, and of the enemy against whom it is fought.

(b) The general war plan of the government.

(c) Diplomatic considerations.

(d) The radius of action of the bomber aircraft available.

(e) The strength and efficiency of the enemy air defence.

(ii) Subject to such restrictions as may be imposed by any of the above conditions, objectives should be selected the bombardment of which will have the greatest effect in weakening the enemy resistance and his power to continue war.

4. The question whether air power can be applied most effectively in direct support of naval or military operations will depend upon the general plan of campaign, and upon geographical and other considerations but, where important centres of production, supply, transport, and organization, vital to the maintenance of the enemy fighting forces, are exposed to effective attack from the air, the bombardment of the most vital and vulnerable of these centres may be more effective and decisive than the direct attack on naval and military forces.

5. The support and maintenance of its fighting forces by a highly developed nation is a very serious problem, which enlists its whole resources and requires from it both high morale and the utmost physical energy. A nation's support to its fighting forces is given chiefly by means of the production and supply of war material and other commodities essential to the successful prosecution of war.

6. In order that these national efforts may be utilized, organized systems of production, supply, communication and transport have to be set up, and these inevitably become delicate owing to the tremendous strain thrown upon them. Such systems have their nerve centres, main arteries, heart and brain. If these are exposed to air attack, the continual interruption, delay and disorganization of the activities of these vital centres by sustained air bombardment will usually be the most effective contribution which can be made by air power towards breaking down the enemy's resistance.

7. In a campaign against an under-developed country where such important centres do not exist, it may never theless be found that there are other centres whether of national organization or of production or storage of the principal resources upon which the maintenance of the country's resistance depends, which are open to air attack. In certain circumstances, however, it may be desirable to use air power in more direct support of the naval or military operations.

8. In a war against an enemy air power the most effective direct assistance which an air force can render to naval and military operations will usually be the establishment of local air superiority in a sufficient degree to assure freedom of action to the aircraft co-operating with those services. Air superiority will also be of particular importance in the early stages of a war, to cover and facilitate the mobilization and movement of troops.

9. Objectives for air bombardment should always be selected mainly with a view to their influence upon the attainment of the principal aim in air warfare.

10. If the enemy's aircraft production plants and big depots can be reached, they provide favourable objectives for attack.

11. (i) Sustained air bombardment of the enemy's aerodromes may also be effective when they are within range, in particular when :

(a) material loss cannot be readily replaced ;

(b) aerodromes are overcrowded, or few in number ; and when alternative sites are very limited,

(c) hangars are close together, or inadequately protected.

(ii) But where enemy aerodromes and landing grounds are sufficiently numerous to allow frequent change of locality, are well organized, protected and defended, and where losses can be quickly replaced, they are not a particularly favourable objective. In such circumstances direct attack on the enemy air force on the ground will not be the most effective means of using air bombardment. It will usually be possible to find more vulnerable and important objectives elsewhere, such as the vital centres of the enemy.

12. As explained in Chapter VII, local air superiority at the decisive point of the naval or land operations may be more readily gained by diverting enemy aircraft from those localities to defend their own important centres against air attack and thereby weakening their forces elsewhere.

The Effect of Air Bombardment

13. Moral effect.—Although the bombardment of suitable objectives should result in considerable material damage and loss, the most important and far-reaching effect of air bombardment is its moral effect.

14. The moral effect of air bombardment is always severe and is usually cumulative, proportionately greater effect being obtained by continuous bombing, especially of the enemy's vital centres : for instance, the continued air bombardment of an aircraft production plant or a dock area where large quantities of war material are being handled, each centre being essential to the maintenance of the enemy fighting forces, may have a serious moral effect on the workers at those centres and on the fighting forces, of greater importance than the material damage inflicted.

15. To produce and handle large quantities of war material, the employment of workers of various categories is necessary and the effect upon their morale when exposed to air attack is to compel them on the first warning of an air raid to leave their work and to take refuge. The more frequent these stoppages, the more will the work and the systems contributing to the supply and maintenance of war material be disorganized. A single air raid on such vital centres may bring work to a standstill over a large area during the whole period of the raid and prolonged attack consisting of air raids at short intervals may be expected to result in such dislocation and confusion as a consequence of the continual stoppage of work and the strain on the workers, that supplies essential to the successful continuance of operations will not be forthcoming. Such results are far more important than the actual physical destruction and damage caused by air bombardment and will react upon the morale of both the enemy nation and its fighting forces.

16. The ideal objective is one recognizable and vulnerable, the successful attack on which, in furtherance of the policy of the Government, may at the moment contribute most effectively to the breaking down of the enemy's resistance. The selection of objectives, whether they be naval, military or air organizations or centres of production, can only be made as the result of an intimate and accurate knowledge of the various organizations of the enemy nation and of the measures that have been taken to avoid or minimize the results of air attacks. Such knowledge can be gained only by a comprehensive and careful study in time of peace and by the study of developments in war.

17. Material effect.—Material is of value only if it is situated where it can be usefully employed. In certain circumstances and in the case of certain kinds of material, it may be easier and more economical to prevent or delay the transportation of supplies than to attempt the destruction of the material itself, and in so isolating the supply or source of supply to achieve a result equivalent to the destruction of the mass of material cut off. The destruction of a transport system, however, is difficult.

18. Effect upon railways. The disruption of the permanent way of a highly organized country is difficult to achieve, and such damage as can be done is easily remedied. The damage of the track at junctions is more serious, but ample repair facilities will usually be available at these centres. Bridges, if destroyed, would cause an effective block, but they present a small target for bombs except where low altitude attack is practicable, and are difficult to damage except with the heaviest bombs.

19. Rolling stock is often insufficient to meet war requirements ; it is vulnerable to attack and difficult to replace. If it is damaged on the permanent way, particularly when at a distance from repair facilities, in a cutting or on a bridge, it is likely to cause a block which will require time and labour to clear and which in the meantime offers a mark for subsequent attacks.

20. (i) The most vulnerable points in a railway system are the centres of railway activity where delay may be caused such as the control centres, signal system, power houses, water supply, transit sheds and goods depôts.

(ii) In less highly organized countries where long distances may be covered by a single track, and where repair facilities are few and far away, a railway line may be an important objective very difficult, if not impossible, for an enemy to protect throughout its length, and liable therefore to low altitude attack at a number of different points. A train derailed in such circumstances, or the damage which could be caused by a heavy bomb accurately placed, may interrupt supply for many days.

21. Effect upon road transport.—Road transport is vulnerable to air attack when it can be interfered with at points of congestion, terminal points, depots or parks or at a road cutting where the clearance of a wreck is likely to be difficult.

22. Effect upon sea and inland water transport.—(i) Shipping is very vulnerable, and harbours, canals and other waterways may be blocked by sinking shipping in them. Similarly, sinking ships in docks or at wharves may put the docks or wharves out of action for some time.

(ii) Locks, docks, and wharves are in themselves difficult to damage, but they are usually the focal points of the transport system and centres of accumulation of material and stores, which provide favourable objectives for air bombardment.

The Security of Bomber Formations

23. (i) The fighting strength and security of a bomber formation depends mainly upon :

(a) Good leadership.

(b) The drill, discipline and cohesion of the formation.

(c) The skill, alertness and initiative of the air gunners.

(ii) A bomber formation can develop a formidable concentration of fire, which, combined with effective tactics and a high standard of drill and discipline, provides it with great power of resistance to attack.

24. When, owing to the strength of the hostile defence, the casualties caused by enemy fighters become excessive, the remedy should first be sought in the improvement of the fighting efficiency and fire effect of the bomber formations themselves, rather than in the provision of escorts.

25. Escorts.—The use of fighter aircraft as escorts to bombers gives rise to difficulties. Single-seater fighters are unsuitable for the purpose ; to be effective, they can only employ offensive tactics against the enemy, and if attacked from behind they must turn and fight. Hence they are easily drawn off and separated from the bombers whom they are intended to protect.

Two-seater fighters are more suitable but, if they adopt offensive tactics against the enemy, they are also liable to get separated from the bombers, and if they adopt defensive tactics they are confined to action which could equally well be performed by a formation of bombers themselves.

26. (i) Evasion.—The ease of evasion in air warfare favours the use of this form of security. By flying at great altitudes the chances of avoiding the enemy are increased and both the strength and duration of the enemy interference are likely to be reduced. On the other hand high-altitude flying is a strain on the personnel and may decrease both the weight and accuracy of the air bombardment.

(ii) Other factors favouring evasion or avoidance of action are :

(a) The use of clouds or darkness for concealment. Clouds, although limiting the height from which aircraft can drop their bombs, are of use in assisting the attack to achieve surprise and in concealing the strength and the direction of the approach and return of the attackers. Darkness also, by careful timing of attacks, may be used to conceal the approach or return of raids ordered for dawn or dusk.

(b) The selection of routes through zones in which our own fighter patrols are operating and the avoidance of localities where the enemy is known to have a strong defence.

(c) The avoidance of any tendency towards routine both as regards time and route in carrying out attacks.

(d) The co-operation between operating squadrons either to insure that attacks are so timed that successive raids arrive when the enemy defensive fighters have landed to re-fuel after meeting a previous attack, or to bomb widely dispersed objectives in order to induce the enemy to split up his forces in an attempt to defend scattered localities.

(e) The employment of light fast bombers operating from great heights to carry out feint raids in order to lure the enemy fighters into the air and tire the defence before the main attack is made.

(f) The frequent and punctual circulation of accurate meteorological information and intelligence regarding the enemy's air activity.

The Conduct of Air Bombardment

27. Sustained attack for moral effect.—Against all objectives where moral effect is the main aim, air bombardment should be as sustained as possible. Sustained bombardment is also necessary where it is desired to force the enemy to divert aircraft to the defence of the objectives attacked.

28. (i) Attacks, once begun, should be continuous and intense until the required effect is produced. It may sometimes be possible to create the effect of continuity, particularly at night, by the use of delay action bombs fused to explode at intervals. Moral effect (especially upon disciplined bodies) cannot, however, be attained without inflicting casualties and material damage.

(ii) Sustained bombardment will entail attacks at intervals according to the nature of the objective. The more frequent the attacks the smaller will be the formations taking part, and therefore the degree to which air bombardment can be sustained will depend upon the strength of the enemy resistance, as well as upon the radius of action of the aircraft employed.

29. Cloud flying.—Weather conditions play a very important part in sustained attacks. In the meteorological conditions prevailing in the British Isles and Northern Europe, sustained air bombardment is only possible if the bombers can be navigated to their objective through and over cloud and fog. In these latitudes the success of air bombardment will depend upon the navigational skill of the pilots, and an important criterion of the efficiency of an air force will be its ability to carry out long distance operations in almost any weather.

30. (i) Concentration of effort.—Attacks should be concentrated against one type of target or one kind of supply, where possible, with the intention of causing a thorough dislocation, or a complete stoppage of a particular production or supply.

(ii) For example—If bombing attacks, which are part of the operations to secure air superiority, have as their object the restriction of output of aircraft, it may be more economical and equally effective to confine attacks to those few plants which produce one essential component of the aircraft, and so to secure a far greater concentration of effort on fewer targets than would be possible if effort was dissipated in attacking several plants, each producing different components.

(iii) Similarly, the successful attack of selected plants concerned in the production of explosives would result in the restricted output of ammunition and this in turn would reduce the value of a large part of the output of guns and other firearms.

(iv) Finally, in certain circumstances, such as in operations in conjunction with the army, it may be desired to prevent supplies or important war material reaching the enemy fighting line on a particular day. This may best be achieved by attacking them over the whole period that they are on the move, i.e., at the supply bases, while in transit by train, at the railhead, and finally while in transit by road, objectives being :

(a) base depôts on the first day ;

(b) trains or selected spots on the railway lines of communications on the second day ;

(c) railheads and the road transport systems on the third day ; or at periods varying according to the speed at which the particular supplies or war material move along the lines of communication.

31. Mass attacks.—(i) Mass attacks delivered by a large concentration of aircraft, operating in suitable tactical formations and arriving over the objective at suitable intervals, are less costly in casualties than sustained attacks carried out by small formations of bombers.

(ii) They are particularly useful against " fleeting opportunity " targets, and may also be used where the main object of the attack is material damage. Since the number of aircraft taking part tends to give confidence to the crews, and is correspondingly embarrassing to the defence, mass attacks may be used with advantage where accurate low altitude bombing is required, each sub-formation descending to drop its bombs in turn while the other formations maintain a higher altitude to protect the bombers from attack by hostile aircraft. The moral effect of bombing is increased if large formations are seen to be operating from low altitudes.

32. (i) The altitude for air bombardment.—The altitude at which bombing attacks should be delivered will vary and will depend upon:-

(a) The nature and importance of the objective and its distance over enemy territory.

(b) The strength of the enemy resistance.

(c) The state of the morale of our own and the hostile air forces.

(d) The weather.

(ii) The advantages of bombing from medium or low. altitudes are :

(a) Greater bombing accuracy.

(b) Greater moral effect.

(c) Low bombing tends to foster and maintain the offensive spirit.

(iii) As against the above advantages if the enemy have superiority in air fighting and a powerful anti-aircraft defence, the bombers may be so harassed that their bombing will be inaccurate.

33. Methods of attack.—By day, bombing should normally be carried out in formations, and bombs should be released upon a signal from the leader. A rendezvous should always be selected to facilitate rallying and the resumption of close order, should it be necessary for aircraft to break formation in the attack.

34. Night attacks may be carried out by single aircraft leaving their aerodrome at irregular intervals, flying at different heights and working independently. Continuity of attack should be the aim of the programme of raids, but the moral effect will be increased, if occasionally the intensity of attack is increased by two or more aircraft operating together or in quick succession.

35. Photographic reconnaissance.—Bomber formations should always include at least one aircraft carrying a camera. The extent of the damage caused by the attack will only be revealed by a careful study and a skilful interpretation of the photographs taken shortly after a raid. Upon the deductions made from these photographs a commander may decide whether a further attack is necessary. When incendiary bombs have been used, it may be advisable to send out a special photo-graphic aircraft some hours after the raid has taken place. To obtain records of the results of night raids the camera aircraft should reach the objective as soon as light renders photography possible ; under favourable conditions such photographs may be taken at night.

36. Classification of targets.—Targets for air bombardment may be grouped roughly into five classes, according to the type of bomb which would be most effective against them, i.e.,

Low Flying Attacks

37. This term is usually applied to attacks on naval and military objectives by low-flying aircraft (generally of the fighter type) using machine guns and small bombs. Both the moral and material effects of such attacks are high, and they are particularly effective against troops in close order in the open and against personnel exposed on the bridge or decks of ships, or in small craft. Their use in support of military operations is dealt with in Chapter XII, paras. 18-20.

38. Low-flying attacks may also be employed against other suitable objectives such as trains, transport both on land and sea, aerodromes and seaplane bases. They are particularly effective when carried out by fighters in conjunction with low-altitude attacks by bombers, on the same objective as the bombers, or on anti-aircraft defences in the same locality. At the same time the fighters are available to attack and destroy any hostile aircraft appearing during the course of the operation.