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Lessons Learned at Dieppe (IV)
Timing, Tanks, and Security
364. The Timing of the Assault
(a) In the Dieppe operation the assaults which took place in the first faint light of dawn (i.e. a visibility of 200 yards) succeeded, whereas those that came in after dawn were unable to make so much progress. It would be very unwise however to draw any definite conclusions from these facts because the daylight assaults which were those against the town itself were faced by defences which were far stronger and by difficulties which did not exist on the flanks.
(b) Thus it is considered that the problem whether to land in darkness or in daylight is an open one and that each particular case must be judged in relation to the broad questions stated below :
(i) Do the conditions of tide and moon, and the time which will be taken by the ships and craft on passage permit of a choice between a day and a night assault?
(ii) Do the circumstances of the operation indicate that a night assault will give a reasonable chance of tactical surprise ? If the answer to this question is in the affirmative, then it is considered that a good many risks and disadvantages can profitably be accepted in order to gain surprise. In this connection, the importance of having vessels and craft of sufficient speed is to be emphasized for good speed will very often not only make an assault possible that otherwise would be impracticable, but in many cases will achieve the additional advantages of a tactical surprise.
(iii) If a daylight assault is thought best, can it be said that the available means of support (including smoke) will be sufficient to deal with enemy defences unhampered by darkness?
(iv) If a night assault is thought best, can the following questions be answered satisfactorily?
Is the Naval assault force capable of accurately conducting an approach in the area concerned and does it possess the latest navigational aids necessary to make an accurate landfall?
Is there sufficient time available for the specialised training required by the Naval and Military personnel taking part?
(c) All these questions are comprehensive and each one of them has many ramifications which must be examined by those who have to take the decision.
(d) Before reaching this decision there appears to be one further and fundamental question which the Commanders concerned should ask themselves ; it is this: “Will a night assault allow me to accomplish something which I do not think I can equally well accomplish by a daylight assault ?”
365. The Landing of Tanks in the Assault
(a) At Dieppe the tanks, which were all landed in daylight with the leading waves in the face of defences which dominated the beach and against tank obstacles that had not been breached, found themselves in grave difficulties. The deduction to be drawn is that, unless overwhelming fire support is available, tanks should not be landed until defences have been captured and the obstacles cleared.
(b) The L.C.T. [Landing Craft Tank] offer a big target when used with the assaulting waves and must not be delayed on the beaches beyond the time required to disembark tactically their loads of tanks and other troops if these are carried. At Dieppe they drew most of the fire, and suffered heavily.
366. Beach Reconnaissance
As soon as it is known that a project involving a combined operation is under consideration, the question of beach reconnaissance in all its aspects must be investigated. In many cases, sufficient information can be obtained from existing publications and personal knowledge. As the project develops, the beach reconnaissance plan should also develop, not side by side but ahead of it, so that when the outline planning stage is reached, the reconnaissance of the beach is complete in every detail with photographs, silhouettes and information concerning the nature and slope of the beach and the waters off it, whether tanks and track vehicles can land on it with or without the use of track laying devices, etc. Information concerning the beaches at Dieppe was very complete and much of it was obtained by the study of oblique and vertical air photographs. Naval reconnaissance methods should also be used but care must be taken that they remain undetected.
(a) One of the most difficult problems to solve in the mounting of a combined operation is that of security.
(b) The Dieppe operation was a particularly complex case as it had been mounted, postponed and cancelled before being re-mounted in the form in which it eventually took place. Thus many hundreds of people were aware of the objective and there was clearly a risk that security might have been jeopardised during the 41 days which intervened between the original cancellation and preliminary order to sail the expedition. Very special steps were therefore taken, and it is gratifying to note that all intelligence sources agreed that the landing came as a surprise and that no abnormal manning of defences or reinforcement of the area had taken place.
(c) The conditions of each operation will vary so much that it is impossible to lay down rigid and detailed rules for the maintenance of security. Common-sense and the particular circumstances of the operation must dictate the measures to be taken.
Attention is drawn to the following points
(i) The maintenance of security among the Naval force is more difficult than in the case of the other Services since the relatively higher trained men who man the craft cannot be prevented from indulging in speculation when unusual preparatory steps are being taken. Such steps are usually necessary at a comparatively early stage. Although speculation may be wide of the mark it may easily focus the attention of a trained agent on the ships concerned and he will at once divine what is in the wind. The only persons who can allay such speculation or direct it into harmless channels, are the Captains of the ships concerned. It must, therefore, be a cardinal principle for these officers to be put into the picture before any overt action is taken in connection with an operation.
(ii) The aim should be to disseminate intelligence at the earliest moment without divulging either the date or the place of the operation. Without naming date or place, much can be done to render training realistic by giving units the details of their tasks, the distances they will have to cover, the type of country and obstacles they will have to move over, and the time limit, if any, within which they must complete their tasks.
It will be necessary also to say whether they are to concentrate on day or night work and to indicate whether there will be other units operating on the flanks.
Armed with this information unit commanders will be able to relate their training to actual operational requirements and to concentrate on the subjects that really matter. It is inevitable that those of an enquiring mind will sense that an operation is being prepared but they will not know when or where.
(iii) In certain cases, it may be found possible, without endangering security, to issue maps, models and photographs which bear no names. The preparation of such aids requires time and demands must be foreseen at an early stage in the planning if they are to be of real use.
(iv) It will be necessary throughout the preparatory stage to keep a careful record of all those who are aware of the operation. In this connection the issue of cards bearing the code name of the operation and the name and details of the holder has been found useful. Such cards, the issue of which should be severely restricted, authorise the holder to speak to another holder, but to no non-holder, regarding the operation.
(v) Throughout the preparatory stages, the “G” [General] and “Q” [Quartermaster] staffs of all three Services must work closely together. If this is not the case, it may be found that the most carefully veiled arrangements by one branch are rendered entirely useless, through lack of knowledge on the part of the other.
(vi) It goes without saying that the number of officers in each headquarters who know of the operation should be kept to the minimum.
(vii) The early production of a "cover” plan for the forces engaged including not only their training but their moves is an urgent necessity.
(viii) It must be realized that strategical surprise may be completely compromised and the constitution of the force given away by the use of wireless, particularly in a well-known operational training area, unless this problem is carefully thought out and regulated. The co-operation of units outside the force may be necessary to adjust or sustain traffic at the required level.
(ix) The administrative and movement aspects of the security problem are dealt with in Annex 12, but it may be said here that the issue of large quantities of stores, equipment and explosives to units, ships and craft is apt to provide much cause for speculation and rumour.
(d) The difficulties encountered in trying to select an area in the South of England which can be completely “sealed” appear to be insurmountable. For various reasons it proved impossible to get even an island like the Isle of Wight completely " sealed ” before the operation. Much can be done, however, to offset this disadvantage by the imposition of postal and telegraphic censorship, monitoring of telephone lines and by the installation of plain-clothes police in hotels, public houses and places where gossip is likely to occur.
(e) During the Dieppe operation, complete copies of the Military Force Commander’s Operation Orders were taken ashore. It is not considered that there is any justification for such a step and that only important extracts such as code words or time-tables need be landed. Even in these cases the numbers carried should be reduced to the minimum. Force Commanders, will, in most cases, be well advised to indicate in orders the portions which may be landed, and those who are authorised to carry them. To prevent the enemy being in a position to quote any of these portions which may be captured as being “ official operation orders,” these extracts should be copied in manuscript and have their official headings removed.
368. When to Brief Troops
(a) In the first mounting of the Dieppe operation troops were briefed and embarked on the first day and thereafter had to remain “sealed" for the whole of the five days during which the operation was kept mounted, waiting for the weather to improve. In some of the smaller ships, which were only intended to ferry soldiers across, the discomfort and lack of space and facilities decreased the efficiency of the troops day by day.
(b) It is therefore desirable to refrain, not only from briefing, but from embarking troops until a long range weather forecast shows some prospect of the weather becoming sufficiently settled to give really good chances of the operation coming off shortly after embarkation and briefing. This was done when the Dieppe operation was finally mounted.
(c) The briefing which has to be given to the aircrews and troops of the airborne division is of necessity much more complicated and, at present, the minimum time required is about four days for the aircrews and two days for the troops. Except in periods of set weather no weather forecast can extend to cover so long a period. It follows that briefing for the airborne division has to take place before there is any real prospect of knowing when the operation is coming off. Further, since the aircrews and troops are not embarked in ships but are scattered in camps, efficient "sealings” can only be done at the expense of focussing attention on the imminence of an operation. The time taken for briefing could probably be reduced to about twelve hours for airborne troops if facilities could be made available for the airborne Division to reproduce the requisite number of “models" for simultaneous briefing of all units concerned.
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.
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