Lessons Learned at Dieppe (III)

Artillery, Air, and Naval Gunfire Support

355. Support for the Assault

(a) Leaving out of consideration the long preparatory bombardments for the reduction of “key” major coast defences which would be a necessary feature of invasion plans but cannot, for obvious reasons, be a preface to raids, the assault, in both raids and invasions, of a defended coast requires fire support while it is in progress, unless complete surprise can be obtained.

(b) Surprise is likely to become progressively more difficult with the passage of time, and support fire more necessary as the enemy increases his defences.

(c) If the assault is to take place under fire support, it must, in volume and effect, be comparable to that which would be available to a brigade attacking a strongly defended position in normal land warfare. The latter would, assuming a normal allocation of army field and medium artillery, amount to :

(i)    Close support weapons:  One-6-pounder. for each 100 yards of objective.

(ii)   Neutralising weapons:  One-25-pounder for each 20 yards of objective. 

(iii) Counter-battery weapons: 5-5-inch and 7-2-inch howitzers sufficient to engage each enemy battery covering the assault beaches with 30 rounds every 30 seconds, or a total of about: 140 guns on a brigade front of 2,000 yards.

This figure ignores the support of mortar fire which would be available to a brigade and the greater accuracy of guns on fixed platforms as compared with ship or craft-borne guns, and should then be regarded as a strict minimum.

(d) The equivalent of these weapons must be available in the form of ships or craft used afloat or beached, in addition to self-propelled artillery, to cover the period between the beginning of the assault and the deployment of the artillery of the assault formations.

356.  The Four Types of Assault 

(а) Support for the assault can be most easily studied under four main headings:

(i)   Support by heavy and medium naval bombardment (paragraphs 357).

(ii)  Support by air action (paragraphs 358-361).

(iii) Support by special vessels or craft working close inshore (paragraph 362).

(iv) Military support during landing (paragraph 363).

(b) The bombardment of Maaloy [Måløy] Island by H.M.S. Kenya, a 6-inch cruiser, enabled landing craft to approach within 100 yards of the shore before it was considered necessary to cease fire. This was, no doubt, a special case, for the Kenya had been able to approach within point-blank range without detection. Such good fortune cannot be counted upon in operations against the coast of France and it must be borne in mind that cruisers are very vulnerable. At Dieppe, no ship larger than a Hunt class destroyer could, with safety, have been used, unless recourse had been had to a capital ship. The effect produced by the broadsides of a battleship at close range can justly be described as devastating. It may be recalled that on the 25th April, 1915, during the attack on Gallipoli, H.M.S. Implacable covered the landing at X beach from only 450 yards, firing 10 rounds of 12-inch, 179 of 6-inch and 154 12-pounder shells.

357. Support by Heavy and Medium Naval Bombardment

(a) At Dieppe, the central assaults against the town itself were supported by a short bombardment carried out by destroyers. This bombardment did not provide effective support for the assault. It was neither heavy nor accurate enough to flatten strong defences, nor could destroyers follow the landing craft in close enough to support the actual assault at short range by dealing directly with such elements of the enemy's defences as had survived.

(b) On the other hand, if larger ships could have been employed, and if they could have been supplied with bombardment charges and could either have observed their fire with accuracy or have it observed for them by aircraft, more satisfactory results would have been possible.

(c) Thus the conclusion drawn is that if Naval bombardment is to be an effective means of preparing for the assault and supporting it, the following requirements must be met:

(i)   Cruisers, monitors or even larger ships must be available for support fire, and should preferably be capable of indirect bombardment with air spotting.

(ii)  The position of the targets must be accurately ascertained beforehand.

(iii) Close support fire by special vessels or craft working close inshore with the assault craft is essential. Any smoke-screen laid must be laid clear of the line of close support fire which in its action must be direct.

358. Support by Air Action I.  Support by Cannon Fighters

(a) The attacks on the central beaches and the final assault on the Varengeville battery were both preceded by cannon-fighter attacks. The attack on the Varengeville battery was particularly effective because “B” and “F” Troops of No. 4 Commando waited until the cannon Spitfires went in and shot up the position, before delivering their final assault.

(b) Such support has considerable moral results and is effective in that the enemy’s attention is drawn away for a few invaluable minutes from the craft coming into land or the troops forming up to attack. At the same time, the enemy's attention cannot wholly be given to the cannon-fighters and experience showed that A.A. fire was much less intense than usual.

(c) It must be appreciated, however, that air action of this kind is essentially fleeting in its nature. For instance, it cannot be expected to keep the enemy’s defences quiescent for sufficient time to allow the leading troops to disembark and cut their way through beach wire, mines or other obstacles. Neither can cannon fighters be expected to put fixed defences out of action. Furthermore, cannon-fighters cannot at present operate in close support under cover of darkness and their activities are thus restricted to daylight action.

(d) Lastly, it is particularly necessary for as large a number of close support squadrons of cannon fighters as possible to be available. These aircraft have only a limited range and can therefore normally participate in a programme capable of only limited variation when operating towards the limit of their endurance. Unless a change in the programme is notified a sufficiently long time in advance, the cannon-fighters may be unable to synchronize their attack with that of the assaulting infantry. Cancellation, however, is possible almost up to zero hour and a new attack can always be delivered within 30 to 40 minutes if provision has been made for an adequate number of aircraft.

(e) In these circumstances, it is concluded that support by cannon-fighters should be regarded as a most valuable adjunct to an assault, but that when including them in the plan it must be borne in mind that the effect of their action is likely to be diversionary in character and of only very short duration. Cannon-fighters are rarely competent to silence a strongly protected position permanently.

359. II.  Support by High Level Bombing

(a) The plans for Dieppe did not include high level bombing prior to the assault. Had suitable day bombers such as American Fortresses been available in sufficient numbers this decision might well have been different. In the circumstances, the main objections to support by night bombing were:

(i) Surprise would have been lost because the bombing would have had to take place some time before the assault in order to allow the bombers to get clear of the target area by dawn, and to have been effective, the weight of the attack would have had to be larger than it is in the normal periodic raids on French ports.

(ii) It would be wasteful effort in view of the inaccuracies which must be expected.

(iii) The rubble from damaged houses might fill the streets and prevent the movements of tanks.

(iv) High level bombing was unlikely to damage many of the sea-front positions from which heavy fire was brought to bear on the landing places.

(v) In order to enable H.M.S. Locust and the cutting-out party to perform their tasks, it was necessary to avoid damage to the harbour installations and the power house.

(b) As against these points, however, it may be argued that:

(i) Surprise would not necessarily have been given away had the bombing been part of a programme of attacks on coastal ports, including perhaps one or two previous raids on Dieppe itself.

(ii) Inaccuracies might to some extent have been overcome by the use of a few expert "path-finders” who could have indicated the target by flares.

(iii) Rubble in the streets might not have proved a worse obstacle than the undamaged road blocks and obstruction walls which were encountered.

(iv) Though particular defence positions might not have been damaged the personnel might have been killed or wounded while on the way to man them.

(v) The moral effect of a heavy raid and the dislocation that it causes cannot be overlooked.

(c) The fair conclusion to draw seems to be that the question whether or not high level bombing should be included in the plan is an open one and that no hard and fast deduction should be drawn. Each case must be judged on its merits having regard to the pros and cons mentioned above and to the possibility of diverting bomber effort from other and perhaps more important programmes.

(d) In connection with air support, generally, it is of obvious importance to note the recent developments in daylight bombing and to consider how they may effect the planning of an assault.

(e) It is only fair to add that large scale night bombing of towns in France is against the general policy of His Majesty’s Government, although an exception might have been made in the case of Dieppe had the Force Commanders really wanted it.

360.  III.  Air Attacks on Enemy Reinforcements

(a) Once an assault on any scale has been launched it will almost invariably be important to prevent or at least delay the .move up of enemy reinforcements. If air action to this end is likely to be required, then it must be arranged for in the plan.  Probably the easiest way of doing this is to hold suitable squadrons at call for the purpose and to organise operations by intruder aircraft at night and Tactical Reconnaissance aircraft by day along the likely approaches so that early warning can be obtained that enemy forces are on the move. Tactical reconnaissance by aircraft proved adequate at Dieppe though the casualties suffered were heavier than those inflicted on aircraft employed on other tasks.

(b) There is little doubt that in a large scale operation, or when an assault is made in an area particularly suited to rapid reinforcement by the enemy, air action against enemy communication centres, barracks and camps will have to be undertaken as part of a set programme, which may have to be initiated some days or even weeks before the raid.  When summing-up the relative importance of retarding or preventing the moves of enemy reinforcements it should be borne in mind that though the coastal defences may be formidable, they are fixed in character. Thus, once a breach has been made, the danger of serious counter-attack comes not so much from the garrisons of other fixed defences in the neighbourhood as from mobile reserves outside the immediate area of the assault. These reserves should be attacked from the air as and when opportunity offers.

(c) In these circumstances, accurate intelligence data concerning the location of enemy formations is a necessity if the Commanders are to arrive at the proper decision regarding the allocation of aircraft as between this and other tasks. The ideal to be aimed at is for the presence of reinforcements to be detected by tactical reconnaissance aircraft and subsequently attacked.

361.  IV.  The Scale of Air Support at Dieppe in Relation to the Scale of the Land Operation

(а) It is of particular interest to note that at Dieppe 67 squadrons were employed on various tasks directly concerned with the operation. This was not abnormally high in view of the anticipated scale of the enemy’s air opposition and proved adequate to cover the operation.

That opposition, however, would decrease :

(i) if operations on the same scale took place at several different points;

(ii) if they were continued over a longer period of time thus progressively reducing the enemy’s air resources.

It is pointed out, however, that if more than one assault is delivered simultaneously at several different points, the enemy is free to concentrate all his air forces against any one of them, for it will scarcely be possible for the Royal Air Force, unless its strength is enormously increased, to give the scale of fighter cover provided at Dieppe to all of them at once. Landings must, therefore, take place with a sufficient interval of time between each to enable maximum fighter cover to be given to each landing in turn, or the enemy’s strength in the air must have been reduced before the operation begins. If it is necessary for several landings to take place simultaneously, reliance must be placed on Intelligence and early warning R.D.F. [radio direction finding].  Such information is normally sufficient indication to enable the Air Force Commander to divert fighter cover from one landing to another and, in the case of one landing only, to intercept enemy air forces on their way to the landing. It is, however, emphasised that this method at the present moment cannot be depended upon, though further developments should increase the probability of its successful use.

(b) Enemy air attacks on ships were at times intensive but the volume of A.A. fire achieved by the close concentration of the ships greatly reduced the effectiveness of the enemy’s low attacks. Such concentration of fire may make it possible for air cover to be reduced in its neighbourhood and used for other purposes. Broadly speaking ships and craft were only hit when detached. The moral is “ Unity is Strength.”

(e) The enemy failed at any time to develop serious air attacks against the troops on shore.

362.  Support by Special Vessels or Craft Working Close Inshore

(а) The assaults at Dieppe, particularly on the central beaches, showed in the most clear fashion the need for overwhelming fire support during the initial stages of the attack.  It is during these vital minutes while troops are disembarking, cutting or blasting their  way through wire, clearing beach mines and finding routes over obstacles that the need for close support is at its greatest. At the same time it is during this very period that the  troops are least able to support themselves because there has not been time to organise and deploy supporting arms. The support that is so necessary must, therefore, come from outside sources ; for without it, the assault will almost inevitably lose momentum and may end in a stalemate with the troops pinned to the beaches, unable either to advance or to withdraw. Overwhelming support of the kind now envisaged should not only make the assault possible, but would also be of the greatest value in protecting the craft themselves from being disabled during the final closing on the beach and while beached. 

(b) It is quite certain that the “Support Craft” which are now available do not meet the requirement envisaged in the preceding paragraph. They are too lightly armed and too  lightly armoured for continued action against the type of defences which the enemy have erected at all important points on the occupied coast-line.

(c) It must be remembered that though an assault may take place to a flank of the main objective, it is in itself a frontal attack. Thus, once the assault is discovered, there is  little room for subtlety. The main necessity is to batter a way through in the shortest  possible time.

(d) In order to achieve this object, it is considered that an entirely new type of support vessel is required, which might be described as a shallow-draught armoured gun-boat. There is also  the technical possibility of a specially designed small mobile fort, constructed on lines  permitting it to be brought to the scene of action and there sunk in position for as long  as may be needed, leaving only the gun turret above water. This, however, would, in  the nature of things, be more for barrage and counter-battery work than suitable for  direct close support against beach defences in the opening stage of the attack.

(e) No such gun-boats or mobile forts exist. The need, however, does and it can only be met by new design and new construction. This is a matter not only of real urgency but is one which will grow in importance. There are two sides to the question. On the one hand, each week that passes allows the enemy more time to strengthen the already strong coastal crust through which we must break, before large forces can be deployed. In carrying out this work, we must anticipate that the enemy will naturally give priority to important areas and ports. On the other hand, the necessity on our part to include in any major attack or even in any major raid the very areas which are most likely to be strongly defended, does not grow less.

363. Military Support During Landing

The attacking troops can add themselves to the volume of covering fire developed during the landing in various ways :

(i) Self-propelled mobile artillery provided that it is put ashore immediately will prove of great assistance in covering the initial assault. In addition to fire from specially designed and fitted support craft, such as the L.C.S. (M) and L.C.S. (L), much assistance can also be given by the troops from the actual landing craft. In each of these latter type of craft, one or two Bren guns and, whenever possible, a 2-in. mortar should be mounted ready for use. The Bren guns may be required against either land or air targets while the 2-in. mortar will be particularly valuable in  providing smoke cover and in blanketing searchlights which may open up on the  landing places.

(ii) It is to be noted that firing from landing craft requires a considerable amount of practice and that frequent opportunities for such practice must be arranged during the preparatory training period.

Note: Save for this note, the entirety of this post is a verbatim copy of a section of a document published in September of 1942. The “block quote” feature (brown line in the left margin) serves simply as a means of indenting the paragraphs that begin with lower case Roman numerals.