The Royal Air Force

The following copies of Cabinet papers between Sir Maurice Hankey and Air Marshal Trenchard in April/May 1928 relate to the latter’s submission of a memorandum intended to state the prevailing Air Staff Doctrine. Hankey’s response and Trenchard’s reaction to that response are to be found in National Archives documents, and these have been reproduced below.

TEXT OF A LETTER FROM SIR MAURICE HANKEY, SECRETARY TO THE CHIEFS OF STAFF SUB-COMMITTEE TO AIR MARSHAL SIR HUGH TRENCHARD, CHIEF OF THE AIR STAFF, dated 28 April 1928, hereafter referred to as Letter No. 1

I am returning herewith your very interesting paper on the War Object of an Air Force.

In our conversation yesterday afternoon I undertook to deal with the question under two heads:-

In this letter I am dealing only with the former point, the latter being dealt with in a separate letter Marked No. 2.

I think your best plan would be to circulate the Memorandum officially to the Chiefs of Staff Sub-Committee, covered by a Note recalling the genesis of the question and stating that before taking your final decisions on the doctrine which you lay down for the RAF War Manual you are anxious to discuss the matter at the Chiefs of Staff Sub-Committee, and that your memorandum is intended as a basis for discussion.

On the whole I prefer this method to circulating it privately. The proceedings of the Chiefs of Staff Committee can be very informal when they desire. I am inclined to think that in this case it might be well to have a preliminary discussion, without any Minutes, and it might be worth mentioning this in your covering Note. This is a procedure by no means unknown to Cabinet of CID Committees, or even, on occasions, the Cabinet itself, when rather controversial and difficult matters have to be discussed.

Do not try to settle this particular question in one Meeting. Let everyone express their views on the deal level, and you will probably exercise some effect on one another’s opinion and get halfway to agreement. Then go away and think it over and at the next meeting you may quite likely reach an agreement. That is my advice.

p.s. The other letter will take longer but I hope to send it not later than Monday M.P.A.H.

In this letter I give my personal views on your memorandum, ‘The War Object of an Air Force’. If in some respects they do not square with your own do not be angry. It is no use for me to write unless I speak freely.

I do not object to the terms in which provisionally you state the aim of the Air Force, though I do criticise some of the arguments you use to support it and I think that they carry you a good deal further than does the actual formula you propose.

You examine the matter under three heads, the first being, ‘Does this doctrine violate any true principle of war?’

With this part of your argument I am in general agreement. Not only do I think that it violates no true principle of war, but I agree with you when you say, ‘there is no new principle involved’. (Page E-4) The destruction of an enemy’s base or source of supply or loss of communications has always been recognised as a legitimate objective of war from the earliest times. Scipio Africanae [sic] brought Hannibal to a standstill by capturing his base at Carthagena, Alexander the Great before invading Persia, destroyed the sea power of the Persians in the Mediterranean by occupying the coasts of Syria, Palestine and Egypt and so depriving the fleet of attacks on the coast roads and depots at both ends of the Pyrenees, thus supplementing the action of the Spanish guerrillas in hampering the communications of the French. In the late War we ruined the original German attack on commerce by depriving the enemy of his bases and his means of communications by cable and wireless.

Your own proposal to use the Air Arm in order to break down the enemy’s means of resistance by attacking his bases of supply and his communications appear to me to be on all-fours with these instances (which no doubt could be multiplied indefinitely) of the use of naval and military force for attacks in supplies and essential communications.

The second question you raise is as to whether an air offensive of this kind is contrary to international law or to the dictates of humanity.

Here again, I find myself in general agreement with you. I think, however, that if your policy is carried out the tendency in the future will be to segregate war manufacture and supply as far as possible from the ordinary civil life of the nation. This, however, will be a very slow process and need not trouble us at this stage.

Your third question is as to whether your methods will lead to victory and in that respect therefore a correct employment of Air power. On this third head I think that you exaggerate both the actual power of the Air and its moral effect, and that you underrate the resisting power of a nation which is fighting for its existence or some cause which it rates equally highly.

First, as regards Air Power. At present I think it is admitted that the effective radius of action of aircraft is strictly limited. I do not know what the present limit is nor do I much care. It may be 200 miles or 250. Beyond that distance, however, the enemy’s factories, supplies and communications will be immune from constant attack and only subject to occasional raids such as we had in the late War. Consequently it is only necessary for the enemy to develop his sources of supply and manufacture outside the effective range of your aircraft to defeat your ends. Beyond your effective radius your physical effect will be small, and your morale effect almost nil. London never cared a rap when Hull was bombed and vice versa. I have myself seen men scream with laughter at seeing a Turkish shell burst in a British ammunition ship! That is simply human psychology.

You may of course tell me that in time aircraft will be able to fly much further. No doubt this will be the case. But in order to fly further they will become larger and more expensive. The numbers which nations will be able to maintain in time of peace will become smaller. It will be exactly like the Capital Ship. Before the War I suppose we had fifty, now owing to their greater cost, only twenty. You will not have numbers at the onset of a war to cover the vast spaces of a country like France or Germany effectively. The munitions and supply works will be scattered and you will never be able to find anywhere to deal a decisive blow. Moreover, as you yourself indicate, there will be continued fighting in the air. Both sides will have to divert air energy (using the term in its widest sense) from bombers to fighters. The risks to your long-distance aircraft, which will be making long journeys over enemy territory and will be liable to be encountered and intercepted over vast distances, will be very great.

Up to now I have spoken of the areas outside your effective radius. Even inside your radius of action your centres of production and supply will be scattered. You yourself, in your Memorandum, say that an organized armed force, whether land sea or air, is very difficult to destroy and applying this to the Air Force, you point out how air bases can be camouflaged, and how personnel and material can be well protected against bomb attack, the layout arranged and speed to prevent a difficult target and so forth. You will get exactly the same thing in your national supply arrangements. They will be scattered, camouflaged, laid out with skill and as many of them as possible put beyond your range. Personally I do not think we are doing enough in this direction. We ought to do all we can to encourage every kind of manufacture of war material away from London. We are far too dependent upon Woolwich Arsenal and London resources, it will take years to escape this dependence, but in my opinion we ought to adopt a definite policy of doing so and I wish the Chiefs of Staff would take a lead in urging it.

Even with comparatively short distances of your aerodromes, I cannot but feel the gravest doubt as to whether you do not exaggerate the power of the Air Force. Just about ten and a half years ago Lloyd George and the War Cabinet were considering whether they should stop the Battle of Flanders. Haig was extraordinarily anxious to continue I asked him privately why? He replied that he wanted to capture some ridge from which he could bombard the Roulers – Thooroet Railway only a few miles behind the Front, which was used for maintaining the enemy’s coast section. I asked him privately why he did not use his air forces, of which he had enormous numbers in the Flanders area. He replied that for this kind of purpose the air forces were perfectly useless. Or take the case of Zeebrugge not so many miles from our aerodromes in the coast region. In order to put to sea the German destroyers and submarines at Bruges had to traverse several miles of canal, an obligatory defile where one would think, in theory, they must be intercepted. One would say that all that was needed was for a scouting aeroplane to see the destroyers and submarines coming out of Bruges, to wireless the moves across our lines whence a force of aircraft would descend on these vessels, sink them and block the canal for a month. Yet there is not a single instance, so far as I know, in the whole War of such an interruption. I could multiply these things indefinitely. The Germans never prevented us from using Dunkirk. They never interfered in the smallest degree with our traffic in the Thames though they were constantly flying over our ships and I have myself counted several hundred merchant ships lying in the Downs. They tried once or twice to attack merchant ships but nearly always missed their target. I remember well some bridge in the Lille region, which our soldiers wanted to have bombed. It was attacked again and again but traffic was never interrupted across it. Every time I crossed the big railway bridge on the way to Paris after leaving Abbeville I used to see more and more shell holes on the river bank. I believe the bridge was never hit.

Even admitting an advance has been made since the war in the accuracy of shooting, the power of your bombs, and so forth, I have seen no evidence of anything which would justify us in discarding the experience of the War in this respect. Even if your highly trained professional airmen can make better shooting than in the past, in time of war they will soon disappear and their places taken, as in the late War, by hordes of gallant but half-trained pilots of the type who, as I have was so often told by an intimate friend in the Flying Corps during the war, simply loosed off their bombs without using their aiming apparatus at all.

As regards morale, I have always thought in my heart, that you over-rate the morale effect of air attacks on a population. I was at the centre of the War the whole time, and although Cabinet Ministers sometimes got in a fret about air raids, it was only because Parliament made itself unpleasant. The result was that a certain amount of force had to be diverted to air defence. I have lately re-read my war diary and I cannot find a single occasion on which I did not brush aside the time spent at the War Cabinet or War Committee on air raids as a sheer waste of time. Although I several times visited the attacked quarters and saw the destruction after the event, and although I and my family were within a short distance of one of the most destructive attacks made I never regarded the morale effect very seriously. Of course it has increased but I think that, to describe it as ‘overwhelming’ as you do on Page 7, is an abuse of language. You yourself admit that the rifleman or the sailor will stand the fire because he is disciplined. The only reason we never tried it in the late War was that we never really had the need. You will of course get particular areas where temporarily you will have panic, just as you can cause panic amongst the best disciplined troops. But you will never drive a determined nation to universal panic. Hull will always jeer at London and vice versa. One saw in France peasants and villagers living for years within the most dangerous zones. I remember well, as late as 1918, being taken with the utmost precautions up a slag heap, at the foot was a half-ruined cottage; the children were playing at the door and the peasant was ploughing his land at the foot of the slag heap. They had been there the whole War. Civilians do not differ essentially from soldiers and are not going to be beaten by sheer bluff, if their hearts are in the war.

To summarise, then, I do not dispute the main conclusion you reach, which seems to me both moderately and modestly worded. I do not see how it can be claimed that you violate any principles of war. I do not think that you necessarily violate the laws of war or the dictates of humanity though you may easily be led by inaccurate intelligence to cross the borderline of humanity. I do not think though that when you talk of securing victory by Air Defence you pitch your case too high. In a word I support your theory but I regard the Air Force merely as one of many means of exercising pressure on an enemy e.g., sea power and blockade, the defeat of his armies and Air power. It is not by any one, but by a combination of the three that we must seek to overcome a really determined enemy. I believe you would really strengthen your case if you would recognize this principle and recast your Memorandum so as to make clear that it is rarely, if ever, a sole means of winning a war, though it is an important contribution.

What we really want is an Imperial Defence Manual into which the other three would be fitted.

Yours ever,

Signed P.A. Hankey

P.S. Please don’t be cross with this note. It is exclusively my own and I have consulted no one in writing it.

Appendix Q

Correspondence Relating to the Cabinet Memorandum, ‘The War Object of an Air Force’