Official Records
ADM 239/261: The Fighting Instructions
Section XX- Convoy Defence
Updated 24-Apr-2005

SECTION XX.-PARTICULAR OPERATIONS (10)
CONVOY DEFENCE

CONTENTS

SECTION XX.-PARTICULAR OPERATIONS (10)

CONVOY DEFENCE

OBJECT
625. WIn convoy defence there is only one object, namely-the safe and timely arrival of the convoy at its destination.

GENERAL PRINCIPLES OF DEFENCE
626. The sailing of a convoy without gaining at least local command of the sea is to court disaster. The "safe and timely arrival" of any convoy is best assured if all contact with the enemy can be avoided. Therefore, the best and soundest method of protecting a convoy is by avoidance. If evasion is impossible, the convoy may need protection against surface vessels, aircraft, submarines and mines.

627. A convoy which is well handled and organised can do much to protect itself. Naval forces allocated for convoy defence may be used for close escort or distant cover. If distant cover is adopted, it will still be necessary for a small force to accompany the convoy to give loal protection ; the normal protection against mines is paravanes, though in special cases sweeping operations may have to be undertaken.

EVASION
628. Success in avoiding enemy forces may be achieved by maintaining secrecy concerning sailing, careful routeing of the convoy particularly in an ocean passage, and by the employment of air reconnaissance. In narrow seas evasion is more difficult, especially where the enemy can use aircraft. Narrow and dangerous areas should be passed during dark hours.

MANOEUVRE
629. Zigzagging at the highest speed available and rapidity of manoeuvre will provide some measure of protection against submarine and air attacks. The Mercantile Convoy Instructions (C.B. 1921) recommend a broad-fronted formation for ships in convoy, the maximum number of merchant ships in a column being four. This formation offers the most difficult target for submarine attack and the best facilities for station-keeping. Owing to the slow speed of the average convoy all possible measures should be taken to shake off shadowing vessels, especially submarines. If practicable, a large alteration of course should be made after dark; failing this, enemy submarines may draw ahead during the night and be in a position for attack at dawn.

PROTECTION OF A CONVOY BY A SMALL FORCE
630. On occasions when a heavy scale of attack is not expected, only a weak escorting force may be detailed ; at other times only a small protecting force may be available. In these circumstances, close escort should be adopted, and vessels disposed to counter the most dangerous form of attack expected.

631. It will be seldom that a small force will have the means to provide all-round air or surface reconnaisance, attacking forces are therefore likely to achieve surprise. For this reason the Senior Officer of the escort must issue a pre-arranged plan of action to his force ; failure to do so may lead to disaster.

632. On sighting an enemy ship, the primary duty of the escort is to make an enemy report. This may lead to the attacking force being brought to action by superior friendly forces in the same area. A convoy will always tend to hamper the mobility of its escort ; once the enemy has been sighted, the escort must try and obtain sea room in which to fight the enemy without interference from the convoy.

633. In the case of attack by submarines, the escort should be guided by the instructions in the Manual of A/S Warfare (C.B. 3024) , Chapter III.

634. Attack by superior force. If the enemy is in superior force, the ships in convoy should be ordered to scatter and the escort to concentrate. The scattering of the convoy will impose dispersion on enemy forces if they endeavour to attack it ; concentration of the escort may give it local superiority if the enemy adopts dispersion. The escort should guard agains being led away from the convoy, and thus exposing the latter to unhampered attack by comparitively weak enemy units. Touch should be maintained, if there is a possibility of the enemy being brought to action by reinforcements.

PROTECTION OF A CONVOY BY THE COVER METHOD
635. In the cover method, the convoy is left with a small escort, sufficient to protect it against the lighter forms of attack, while the main force occupies a covering position well clear of the convoy, where it can be reasonably certain of intercepting any large enemy force, which may be searching for the convoy to destroy it. The disadvantage of this method is that interception of the enemy will not be reasonably certain unless the weather is suitable for air reconnaissance, and intelligence from outside sources reliable. The covering force should always be in close touch with the convoy at dawn.

636. The cover method has the following advantages:-

(a) The enemy, when intercepted, will be at some distance from the convoy, which can be given ample warning.
(b) The action is entirely unhampered by the presence of the convoy.
(c) The convoy, having only a small escort, is more difficult to locate.
(d) It might bring about a fleet action, which would be the decisive factor in the war.

637. The main fleet would normally occupy a position about fifty miles from the convoy in a direction towards the enemy's most probable line of approach. Should contact with the enemy be made, the tactics to be adopted would follow normal lines.

638. Ships of the escort with the convoy should be disposed to give protection against the forms of attack expected. If possible, the convoy should be provided with some form of extended screen to give warning of the approach of enemy surface vessels and aircraft that have not been located by the main force.

CLOSE ESCORT BY THE MAIN FLEET
639. When a large fleet is employed in the protection of an important convoy, close escort is the only method to meet all contingencies. Although the convoy will be easier to locate, and its presence will considerably hamper any action fought by the fleet, there will be less risk of a serious disaster to the convoy. Furthermore, if the enemy is met in force, the whole fleet will be available for action, instead of being divided as in the cover method.

640. In the close escort method two conditions must be considered:-

(a) Clear weather by day, and
(b) Night or thick weather by day.

641. By day, in clear weather, a cruising disposition similar to that shown in Diagram III on page 127 might well be adopted. In the positions shown, capital ships and cruisers would be well placed to meet attack by surface vessels or aircraft from all directions. All-round air reconnaissance would be required and an anti-submarine screen to cover the whole front of the convoy and battleships. If air reconnaissance cannot be provided, an all-round extended screen of destroyers will be required. If submarines are available and the convoy speed will not exceed 15 knots, they may prove very valuable as distant look-outs. They should achieve priority in sighting, and by diving after making enemy reports, they may be in a position to attack enemy ships closing the convoy.

642. On a large enemy force being located in the vicinity of the convoy, immediate steps should be taken to concentrate the main force, the convoy being manoeuvred clear of the area of action. When attacked, the escorting force should not be drawn away, leaving the convoy open to attack by other enemy ships, but should endeavour to ensure that the convoy does not come under fire from attacking vessels. It should be remembered that ships employed on close escort duties will always have the advantage of working on interior lines.

643. In thick weather and at night it will be desirable to have a screen of cruisers and destroyers surrounding the convoy, units being stationed in accordancve with the principles of night screening. In these circumstances the positions occupied by the captial ships would be similar to those in clear weather conditions by day. Aircraft carriers should be stationed between pairs of capital ships when no flying is taking place.

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