REFERENCE DOCUMENTS & RESOURCES - OFFICIAL ADMIRALTY DOCUMENTS
ADM 239/261: THE FIGHTING INSTRUCTIONS, 1939 (C.B.04027)
Updated 31-Mar-2007

This document is a modern transcription of a portion of Admiralty record ADM 239/261. This lengthy document contains the Admiralty's official fighting instructions. The original file is held at the The National Archives at Kew, London. This Crown Copyrighted material is reproduced here by kind permission of The National Archives.

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- Pages 9-28 -

CRUISING, RECONNAISSANCE AND SHADOWING

SECTION II.-CRUISING

CONTENTS

Clause Subject
35-36
35
36
 
37-57
37
38-41
42-43
44-51
52-53
54
55-57
 
58-78
58
59-60
61
62
63-64
65-67
68
69-71
72
73-75
76
77-78
 
79-91
79-80
81-82
83-84
85-86
87
88
89
90-91
 
92-94
 
95-100
 
101-107
101
102
103
104
105
106
107
 
108-121
108
109
110-113
114
115
116-117
118
119-121
 
122-125
122
123
124-125
 
126-134
126-127
128
129-130
131
132
133
134
 
135
 
136
137-139
GENERAL.
Entering and leaving harbour.
Speed when cruising.
 
PROTECTION AGAINST SUBMARINES.
The Sighting of submarines from aircraft.
Employment of A/S air patrols.
(blank)
Anti-submarine screens.
Asdic striking forces.
Zig-zagging.
(blank)
 
PROTECTION AGAINST AIR ATTACK
General
Forms of air attack.
Principles of defence against air attack.
Warning of air attack.
R.D.F.
The air warning screen.
Action by the main force against air attack.
Avoiding action when attacked by aircraft.
Protection of submarines in company with the fleet.
Action by vessels on a close screen during air attack.
Action by fighter patrols and other aircraft.
(blank)
 
PROTECTION AGAINST MINES.
General.
Methods of providing security.
Destroyer searching sweep.
Destroyer protecting sweep.
Paravanes.
Speed in mined waters.
Reporting mines.
(blank)
 
PROTECTION OF AIRCRAFT CARRIERS. (Click here)
 
ALLOCATION OF FORCES FOR SCREENING DUTIES. (Click here)
 
CRUISING DISPOSITIONS.
General considerations.
Cruising dispositions when air reconnaissance is impracticable and air attack improbable
Cruising dispositions when air reconnaissance is available and air attack expected.
Cruising dispositions in restricted waters.
Cruising dispositions when mines are expected.
Cruising dispositions-position of aircraft carriers.
Cruising dispositions at night.
 
NIGHT SCREENS.
Considerations affecting the principles of night screens.
Small screens inside visibility distance.
Large screens.
Stationing of 8-in cruisers at night.
Position of counter-attacking units.
Action when an outer screen and counterattacking forces are employed.
Action when a single screen is employed.
(blank)
 
PROCEDURE WHEN MERCHANT AND FISHING VESSELS ARE MET AT SEA.
Action when cruising with the fleet.
Action by detached units or ships on patrol.
(blank)
 
DEGREES OF READINESS FOR ACTION.
General.
First degree of L.A. readiness. First degree of A.A. readiness.
Second degree of L.A. Readiness Second degree of AA readiness.
Third degree of L.A. Readiness Third degree of AA readiness.
Fourth degree of L.A. Readiness
Fourth degree of AA readiness.
(blank)
 
DARKENING SHIP. Click here
 
GAS WATCH. Click here
(blank)

SECTION II.-CRUISING

GENERAL

ENTERING AND LEAVING HARBOUR
35.
When operating from a fully functional protected naval base the Admiral, having ascertained from the Naval Officer-in-charge the degree of security to be expected in the approaches from enemy mines and submarine, will take any further necessary action to provide extra security from fleet resources. The action to be taken will include antisubmarine searches or patrols by destroyers and aircraft, and minesweeping measures.

SPEED WHEN CRUISING (Time not being an essential factor)
36.
Taking into consideration economy in fuel consumption, asdic operating, efficiency in protection against mines and handiness in manoeuvring when countering air and torpedo attacks, a speed of the fleet between 16 and 18 knots is the most suitable.

PROTECTION AGAINST SUBMARINES

THE SIGHTING OF SUBMARINES FROM AIRCRAFT
37.
It is only in very favourable weather conditions that an aircraft can count on sighting a submarine before the latter had sighted her and dived. However, the fact of making a submarine dive reduces her mobility by 75 per cent. and thus her potential danger. In clear weather aircraft may sight submarines on the surface at a distance of six miles ; at periscope depth up to two mile ; below periscope depth from overhead in a clear unbroken sea.

EMPLOYMENT OF A/S AIR PATROLS
38.
Aircraft may be employed on Outer and Inner A/S air patrols.

(a) The Outer A/S Air Patrol. The function of this patrol, which keeps under observation an area to a depth of 20 miles ahead of the extended screen, is to force submarines to dive before they have sighted any surface units. Submarines sighted should be attacked and reported, and subsequently followed until destroyed or no longer a danger to the fleet (see Signal Manual, Chapter XVII).

(b) The Inner A/S Air Patrol. The function of this patrol, which covers the area between the advanced asdic screen and the main force, is to co-operate with surface screening vessels in the destruction of submarines approaching a position from which they can attack the main force. The inner A/S patrol aircraft should also assist aircraft of the outer patrol and advanced screening vessels, which have dropped back in contact with a submarine in their area.

39. Normally the outer patrol will be of greater importance than the inner, as a distant report of a submarine will enable the main force to take evading action ; whereas a report from the inner patrol may not be received in time for such action to be taken.

40. If the enemy is aware that force at sea is restricted in its movements for geographical or other reasons, or enemy submarines are operating with surface or air reconnaissance, it is probable that they will keep a diving patrol. But with the main force unrestricted and surface or air reconnaissance unlikely to be available to enemy submarines, it is probable that they will keep a surface patrol. These considerations should be borne in mind when sufficient aircraft are available to maintain both types of patrol.

41. If an aircraft carrier is in company with the force at sea, carrier-borne aircraft should be provided for the A/S air patrols required by the Admiral. In the absence of an aircraft carrier, and if the weather is suitable for recovery, catapult aircraft may be employed. Single-seater aircraft are unsuitable for both types of A/S air patrol ; two- or three-seater aircraft should be used. The patrol procedure to be carried out by aircraft on A/S air patrol duties is laid down in the Fleet Tactical Instructions.

42. Blank

43. Blank

ANTISUBMARINE SCREENS
44.
Types of A/S screens. A force may be screened by cruisers or destroyers employed on all or any of the following screens (see Signal Manual, Chapters X and XI):-

(a) Extended screen.. .. .. .. .. .. .. .. .. .. .Cruisers or large destroyers.
(b) Advanced asdic screen .. .. .. .. .. .. .. Destroyers.
(c) Close asdic screen .. .. .. .. .. .. .. .. .. Destroyers.

45. Additional protection can also be provided by stationing vessels inside the close asdic screen, to act as a physical obstruction to submarines which have succeeded in evading the asdic screens in bad asdic conditions.

46. The main force should always be provided with a close asdic screen. If insufficient vessels are available to form both the advanced and close asdic screens, the advanced asdic screen should be abandoned. Spare destroyers can be formed into asdic striking forces (see Clauses 52 and 53).

47. The Extended Screen. The extended screen is intended primarily for reconnaissance duties. Ships on this screen should, however, be guided by the following instructions if a submarine is encountered:-

(a) Submarines on the surface are to be forced to dive as soon as possible, to prevent them sighting the main force.
(b) Submarines are to be attacked by gunfire, depth charge and ramming whenever opportunity occurs. Vessels should not, however, leave their stations by more than five miles or close within four miles of an asdic screen.
(c) Aircraft seen to be in contact with a submarine and any submarines sighted are to be reported at once.
(d) Vessels of the extended screen are responsible for passing to aircraft of the outer A/S air patrol all signals that affect them.

48. The Advanced Asdic Screen (see Signal Manual, Chapter XI). The object of the advanced asdic screen is to cover an 8,000 yard torpedo zone with the screen stationed six miles ahead of the unit being protected. Details of the number of destroyers required to give complete protection under various circumstances are given in the Manual of A/S Warfare (C.B.3024). In normal circumstances, two complete destroyer flotillas are required for this duty. If the numbers available fall short of the full number required, it may be necessary to reduce the torpedo zone covered, or the distance ahead of the screen, or both.

49. The function of the vessels of this screen is to detect, counter-attack and report all submarines in a position to menace the battlefleet. A contact is not to be reported to the fleet until it has been confirmed as a submarine. The assistance of the A/S air patrols should be obtained for this purpose.

50. The Close Asdic Screen. The object of the close asdic screen is to prevent a submarine approaching within her maximum firing range from the battlefleet without coming within asdic range of the screen. When asdic conditions are such that reliance cannot be placed on a submarine being detected by this means, it will be desirable to station the screen at such a distance from the battlefleet, that it offers the maximum physical obstruction in the area from which submarines should fire if they are to have a good chance of hitting, at the same time allowing every possible use to be made of asdics in the conditions prevailing. In the former case the centre of the screen should be stationed 4,000 yards ahead, and in the latter case 3,000 yards ahead of the unit being screened.

51. The function of vessels of this screen is to counter-attack immediately any submarine which they themselves sight or detect, or which is being indicated by an A/S patrol aircraft. It must be remembered that the time available for the confirmation of a contact is very short, as the submarine will be rapidly approaching or will have reached its firing position. Any submarine or torpedo sighted is to be reported immediately.

ASDIC STRIKING FORCES
52.
If A/S air patrols are operating and conditions are favourable for sighting submarines from the air, asdic striking forces should be stationed in the vicinity of the extended screen. If these conditions do not exist, the asdic striking forces should be near, but not part of, the close asdic screen.

53. Asdic Striking forces, or in their absence, vessels of the screen may be detached by the Admiral to hunt and destroy a submarine after the fleet has passed out of danger. Unless otherwise ordered, however, asdic vessels are to abandon the hunt and regain their stations when three miles astern of the main force, unless the submarine's position is such that she is a menace to important units operating in rear of the fleet.

ZIGZAGGING
54.
Zigzagging is an essential antisubmarine precaution. Whenever possible all units should zig-zag during daylight or moonlight, whether screening destroyers are in company or not. Instructions for zigzagging are given in the Signal Manual, Chapters IV and XI.

55. Blank

56. Blank

57. Blank

PROTECTION AGAINST AIR ATTACK

GENERAL
58.
When at sea the fleet may be liable to attack by shore-based and ship-borne aircraft. In general, the performance of shore-based aircraft will always be superior to that of aircraft operated from ships. Furthermore, landplanes can be operated in weather conditions when it is impossible to use carrier-borne or catapult aircraft.

FORMS OF AIR ATTACK
59.
The forms of attack most likely to be encountered are:-

(a) Level bombing.-To disable ships by penetration.
(b) Torpedo attack.-To sink a small number of ships, or to cripple a larger number.
(c) Dive bombing.-To disorganise armoured ships and to disable unarmoured ships.
(d) Point-blank attack.-To disorganise the directing and control personnel of ships.

60. Synchronisation of different forms of attack will probably be aimed at, with a view to embarrassing the defence. Experience shows that attacks carried out at late dusk, early dawn or in bright moonlight are more likely to be successful than those in daylight or attempted on dark nights. Details of attack procedure are given in the Air Defence Instructions, Part I.

PRINCIPLES OF DEFENCE AGAINST AIR ATTACK
61.
Attacks by aircraft can be countered by gunfire, manoeuvre and fighter patrols. If these methods are to be fully effective, it is essential that the Admiral should receive early information of the movements of hostile aircraft, and it is fundamental that ships should sight aircraft before they attack. To attain this:-

(a) Highly efficient look-outs are necessary in all ships. Detailed instructions for air look-outs are contained in current fleet memoranda.
(b) Means of obtaining warning of air attacks should be provided for the force at sea.

WARNING OF AIR ATTACK
62.
Warning of the approach of aircraft formations may be obtained from reports received from shore or patrol vessels, from the use of R.D.F., and from ships spread round the fleet on an "Air Warning Screen."

R.D.F.
63.
From trials carried out in ships fitted with R.D.F. it appears that this apparatus is capable of:-

(a) Detecting aircraft on any bearing up to ten miles at 1,000 feet, and up to fifty miles at 10,000 feet.
(b) Distinguishing between large and small formations of aircraft.
(c) Giving an approximation of the course of aircraft formations already detected.

64. Limitations of R.D.F. In its present state of development, R.D.F. suffers from the following limitations:-

(a) It does not distinguish between friendly and hostile aircraft.
(b) In clear weather it cannot give the fleet earlier warning than air look-outs of aircraft approaching below 1,000 feet.
(c) It is unsatisfactory within forty miles of land, especially at night, owing to false echoes from neighbouring hills. This is partially overcome when local conditions have become familiar through operating experience.
(d) The movements of more than two aircraft formations cannot be covered at the same time if their bearings are widely separated.
(e) The actual number of aircraft in any formation cannot be determined.
(f) The operation causes some interference with normal W/T communications.
(g) Use of R.D.F. produces great strain on operators.
(h) It can be D/F'ed by shore stations, or ships with suitable receivers.

THE AIR WARNING SCREEN (See Diagram No. I on page 125.)
65. When R.D.F. is not available in a force at sea and air attack is expected, vessels are required for air warning in sectors not already covered by units engaged on reconnaissance and antisubmarine duties. If numbers permit, destroyers should be stationed as a screen round the fleet, normally at not more than twice visibility distance. Their duty is to engage and give immediate warning of the approach of enemy aircraft. To reduce the chances of aircraft being undetected, the distance apart of adjacent units should not exceed ten miles ; in certain localities it may be desirable to reduce the gaps by closing in the screen or screens. Inside the destroyers, cruisers should be stationed so that they can engage and disorganise aircraft formations on their way to attack the main force. They should also act as V/S linking ships between the air warning screen and the remainder of the fleet.

66. If there is a shortage of cruisers and destroyers, the air warning screen may have to be dispensed with altogether, or only maintained in the direction from which air attack is most expected or least likely to be observed by the main force, i.e., from up sun or an area of low visibility. It will not be required in conditions when attacking aircraft have difficulty in locating surface vessels.

67. The adoption of an air warning screen entails some dispersion of the AA defence of the fleet, and reduces the column of long range fire against aircraft during the later stages of their attacks. There is also a lack of mutual support between ships so spread, and a rapid concentration in the event of unexpected contact with surface forces would be difficult to effect. These disadvantages must be weighed against the advantage of early warning of air attack and the disposition adopted should be that best suited to the situation at the time.

ACTION BY THE MAIN FORCE AGAINST AIR ATTACK
68.
On receipt of an air warning signal or on sighting enemy aircraft, the Admiral will manoeuvre the main force so as to bring the most effective anti-aircraft fire to bear and to present the most difficult target to the aircraft. Fire should be opened by all ships immediately attacking aircraft come within range.

AVOIDING ACTION WHEN ATTACKED BY AIRCRAFT
69. Bombing attacks.
Experience has shown that drastic alterations of course just prior to bomb release do not necessarily embarrass the bomb aimer or reduce the probability of bomb hits. It is preferable to avoid alterations of course which will prejudice the development of effective AA fire. As soon as the direction of attack can be forecasted or observed, course may be altered by Squadron or Divisional Commanders to bring AA armaments to bear against aircraft during their final approach, whether or no any previous action has been taken by the Admiral.

70. Torpedo attack. It is essential that the maximum volume of fire is brought to bear on all attacking aircraft during the approach. Though initial action will normally be taken by the Admiral, Squadron or Divisional Commanders will manoeuvre their columns until shortly before torpedo release, when individual avoiding action will be required.

71. Attack at night. On dark nights, attacking aircraft will have difficulty in locating ships, even if flares and flame floats are used. It will also be difficult for ships to illuminate and engage aircraft effectively. The best policy, therefore, is evasion, which may be assisted by the use of moderate speed to obviate visible wake and funnel smoke, and by efficient vertical darkening. Whenever it appears likely that enemy aircraft will shadow or attack the fleet at night, destroyers should be detailed to extinguish flame floats dropped by aircraft. When it is apparent that the position of the main body is known to shadowing aircraft, one of more vessels on the night screen should be detailed to drop holmes's lights to simulate flame floats.

PROTECTION OF SUBMARINES IN COMPANY WITH THE FLEET
72.
Fast submarines in company with the fleet will be safest from air attack when in close station on the main force, and where they will gain protection from the AA fire of the heavy ships.

ACTION BY VESSELS ON A CLOSE SCREEN DURING AIR ATTACK
73.
In order to provide additional AA fire for those ships of the main force which are most exposed to air attack, and to hamper attacks by torpedo carrying aircraft, a close AA screen is required. Owing to their more powerful short and long range AA armament large destroyers are the most suitable vessels for this duty.

74. As, in the absence of R.D.F., air attacks may develop with little or no warning, it is desirable that units of the close AA screen be stationed in or near the positions where their AA fire will be most effective to the main force. However, it will usually be necessary for vessels to combine the duties of close AA and close asdic screening. When close AA screening positions have been taken up, some measure of protection against submarine attack will still be provided by the use of asdics in those vessels, which are clear of the wakes of other ships.

75. Immediately the approach of an enemy air formation is reported, vessels of the close asdic screen should be ordered to take up close AA screening positions. Detailed instructions for manoeuvring the battlefleet and for vessels of the close A.A.screen during air attacks are contained in the Fleet Tactical Instructions and Signal Manual, Chapter XI.

ACTION BY FIGHTER PATROLS AND OTHER AIRCRAFT
76.
When R.D.F. Is not available but an air warning screen is in operation, warning of air attack will not reach aircraft carriers in time for fighter patrols to fly off and gain the necessary height and position for interception. In these circumstances, as large a proportion of fighters will be maintained on patrol as the number available permits. It must be remembered that it will always be difficult to direct aircraft once air-borne on to attacking formations. When no fighter patrol is maintained, a small number of fighters should be kept ready for flying at short notice to drive odd shadowing aircraft. All friendly aircraft must be responsible for their own safety. On seeing AA fire opened, they should move outside gun range. No reliance should be placed on identification signals being seen in the fleet.

77. (Blank)

78. (Blank)

PROTECTION AGAINST MINES

GENERAL
79.
Mining in depths up to 1,000 fathoms is now possible, consequently the possibility of encountering mines in deep water should not be entirely discounted. In the early stages of a war, however, the enemy may be expected to lay small minefields in shallow and restricted waters rather than in unrestricted ocean waters ; in many parts of the world precautions against mines will be unnecessary.

80. Submarines may be employed by the enemy near to their own minefields, thus it will not be possible to relax precautions against these vessels in waters where mines are suspected. Occasions may arise, however, when a Senior Officer will have to decide which menace is the greater and then take the necessary precautions.

METHODS OF PROVIDING SECURITY
81.
Security against mines is provided by:-

(a) Destroyers searching sweep.
(b) Destroyer protecting sweep.
(c) Paravanes.
(d) Minesweepers.

82. All these methods can be used singly or in conjunction, depending on the number of minesweeping vessels available and the estimated or known risk of encountering mines. Detailed instructions for (a) and (b) are contained in the Signal Manual, Chapter XI.

DESTROYER SEARCHING SWEEP
83.
The function of a searching sweep is to give warning of mines in the line of advance of the fleet so that the main force may be manoeuvred clear of the dangerous area discovered. Destroyers will normally be stationed well ahead of the fleet for this purpose. The efficiency of the search will depend on the number of destroyers available and their distance apart.

84. If destroyers are not available for a searching sweep, a proportion of those stationed on the advanced asdic screen may be ordered to stream their sweeps. Though able to counter-attack submarines detected, these particular vessels would be unable to stop and confirm contacts or to hunt submarines without serious damage to their sweeping gear.

DESTROYER PROTECTING SWEEP
85.
The function of a protecting sweep is to give complete protection to a column of heavy ships or cruisers. The normal minesweeping unit is a division of destroyers, and this number will provide security against mines for four capital ships. If mines are located by the searching sweep, a protecting sweep will normally be formed. Provided the centre of the close asdic screen is stationed at least 4,000 yards ahead of the leading ship of the unit being screened, a protecting sweep can be positioned between the column and the screen, without causing interference to the A/S/ measures.

86. A searching sweep provides some measure of security to a fleet which is zigzagging, whereas a protecting sweep provides none unless the columns being protected alter course in succession.

PARAVANES
87.
All ships carrying paravanes should run them on leaving or approaching a harbour, whether channels have been swept or not ; when a searching or protecting sweep is provided ahead of them ; and in all waters that are mineable.

SPEED IN MINED WATERS
88.
Sweeping devices and paravanes are less efficient at slow speeds, and to cut certain types of mine a minimum speed of 16 knots is required.

REPORTING MINES
89.
On all occasions of cutting or sighting a mine, ships should make the appropriate signal at once (see Signal Manual, Article 171). Other ships should avoid that position.

90. (Blank)

91. (Blank)

PROTECTION OF AIRCRAFT CARRIERS

92. When subject to attack by shore-based or carrier-borne aircraft, protection may be afforded to an aircraft carrier by:-

(a) Stationing her in the line between two capital ships.
(b) Providing a close escort of two cruisers with a good A.A. armament.
An anti-submarine screen consisting of a division of destroyers will usually be required in addition to the cruisers. These destroyers may also provide protection against mines.

93. When there is a shortage of cruisers and destroyers for screening purposes, it will usually be necessary to station the aircraft carrier in the line. The aircraft carrier will normally be stationed immediately astern of the Admiral, in order to facilitate the conduct of flying operations. On receipt of information from the aircraft carrier as to the time, estimated course and speed required for operating aircraft, the Admiral will manoeuvre the column as necessary, ships being ordered to turn together. Detailed instructions for the conduct of ships and screening units under varying circumstances when countering air attack are laid down in the Fleet Tactical Instructions and Signal Manual, Chapter XI.

94. (Blank)

 

ALLOCATION OF FORCES FOR SCREENING DUTIES

95. It will be seldom that sufficient light forces are available to meet all screening requirements. The relative menace of the varying forms of attack must be judged for each particular occasion when a cruising disposition is ordered. In practice, it will often be necessary to provide partial security against two or more forms of attack simultaneously. In considering the measures to counter each form of attack the order of importance is shown below.

96. Submarine attack.

(a) Close asdic screen for the main force.
(b) Asdic screens for the aircraft carriers and battlecruisers.
(c) Advanced asdic screen for the main force.
(d) Asdic screens for squadrons of large cruisers when concentrated.
(e) Asdic striking forces.

97. Air attack.

(a) Close A.A. screen for the main force.
(b) Close A.A. screen for the aircraft carriers.
(c) Air warning screen.

97. Mines.

(a) Paravanes.
(b) Searching sweep.
(c) Protecting sweep.

98. (Blank)

99. (Blank)

100. (Blank)

CRUISING DISPOSITIONS

GENERAL CONSIDERATIONS
101.
When the fleet or any force is at sea, the different units are disposed in relation to the main force for the following reasons:-

(a) To provide the Admiral with early information of enemy air and surface forces.
(b) So that the different types of ships are in such a position that they can bring the enemy to action in the most favourable manner and with a minimum delay.
(c) To enable ships to be in the most favourable positions from which aircraft and submarines can be counter-attacked.
(d) To provide security for the main force from air and submarine attack and sometimes from mines.

CRUISING DISPOSITIONS WHEN AIR RECONNAISSANCE IS IMPRACTICABLE AND AIR ATTACK IMPROBABLE
102.
In this situation the Admiral will depend on surface vessels to provide reconnaissance. Security against air attack is unnecessary, but precautions against submarine attack are required. Under these conditions, Cruising Disposition No. 1 is appropriate.

CRUISING DISPOSITIONS WHEN AIR RECONNAISSANCE IS AVAILABLE AND AIR ATTACK EXPECTED
103.
With air reconnaissance or R.D.F. in operation, a first contact between the enemy and the advanced forces of the fleet is improbable. In these circumstances, units of the extended screen should be concentrated and will cover a narrower front and their distance ahead of the main force should be reduced to increase mutual support. To guard against a surprise attack the Admiral will station available vessels on an air warning screen (see Clauses 65-67). A typical cruising disposition to meet these conditions is shown in Diagram I on page 125.

CRUISING DISPOSITIONS IN RESTRICTED WATERS
104.
When a force is proceeding through restricted waters the chances of submarine attack are increased. Every measure should be taken to provide security against submarines.

CRUISING DISPOSITIONS WHEN MINES ARE EXPECTED
105.
If a force is proceeding through mined waters the front should be as narrow as possible and covered by destroyers carrying out a searching sweep at a considerable distance ahead of the fleet. If mines are encountered, the main force should be manoeuvred to avoid the mined area. If in such circumstances the Admiral attaches greater importance to security against mines than submarines, he may order protecting sweeps for the main force and other important units of the fleet, measures against submarines being correspondingly reduced (see Signal Manual, Chapter XI).

CRUISING DISPOSITIONS- POSITION OF AIRCRAFT CARRIERS
106.
When circumstances permit, aircraft carriers should operate in the line of heavy ships. This position will afford them the greatest degree of security from all forms of attack. If, however, this is not possible, aircraft carriers should operate in waters through which the fleet has passed and as close to the fleet as practicable. By so doing they will be afforded partial protection against submarines and mines. Should the direction of the wind, etc., be such that it is not possible for the aircraft carriers, during flying operations, to remain under the cover of the fleet, each aircraft carrier should be provided with protections against air attack, submarines and mines (see Clauses 92-93).

CRUISING DISPOSITIONS AT NIGHT
107.
Before nightfall the Admiral may be expected to order the main force either to continue through the night in the day cruising disposition or to take up a more suitable disposition for fighting the enemy during dark hours. At night, all capital ships should be in single line ahead, with gaps of about two miles between each division or squadron (see Diagram II on page 126). Aircraft carriers should be stationed between capital ships in the line. This provides a narrow front to a searching force approaching from ahead or astern, ensures freedom of manoeuvre and permits the whole force to open fire on both flanks.

NIGHT SCREENS

CONSIDERATIONS AFFECTING THE PRINCIPLES OF NIGHT SCREENS
108.
If all the light forces are required for attack on the enemy or are not otherwise available it may be necessary for the main force to proceed at night unscreened. Although liable to attack with little or no warning the main force will present a narrow front and enemy light forces approaching from nearly ahead or astern will have difficulty in locating it. If capital ships comprise the main force they should not normally be left unscreened (see Clause 415).

SMALL SCREENS INSIDE VISIBILITY DISTANCE
109.
As an alternative a small screen, consisting of a few destroyers stationed within visibility distance may be used. This as the advantages that some warning of impending attack may be expected, and unobserved torpedo fire at the main force and shadowing of the latter can be hindered. However, there will be little time for avoiding or breaking up an attack, and screening vessels will be liable to be illuminated and fired at by the main force, or other screening units. In order to avoid hampering the main force, it will usually be desirable only to station screening vessels before the beam of the leading ship and on the quarters of the rear ship of the line.

LARGE SCREENS
110.
The conditions that govern the stationing of these screens are:-

(a) There must be ample warning of an impending attack.
(b) The main force must have room to manoeuvre.
(c) The main force's line of fire should be reasonably clear of the defending forces.
(d) Counter-attacking formations must have ample time to attack the enemy before the latter can fire torpedoes at the main force.
(e) The screen must make full use of its offensive power.
(f) The screen should be stationed so that as many directions of attack as possible are blocked in adequate force.

111. The above considerations are to some extent conflicting and the Admiral, when ordering the night screen, will take into account:-

(a) The varying visibility on different bearings.
(b) His night policy as regards evasion or fighting.
(c) The number of screening vessels available.

112. A night cruising disposition for a large force is illustrated in Diagram II on page 126. This is based on the following considerations, which should be used as a guide when ordering a night screen:-

(a) An outer screen preferably composed of 6-in. cruisers.
(b) Counter-attacking forces of destroyers inside the outer screen, and organised in divisions.
(c) Separate units on the quarters to counter shadowing vessels.

113. It is not possible to lay down fixed distances between the battlefleet and counter-attacking forces and the outer screen. In normal visibility conditions, it may be desirable for counter-attacking forces to be just within visibility distance from the battlefleet divisions, the outer screening units being a similar distance from the counter-attacking forces. This will assist screening units to maintain the positions ordered and will facilitate alterations of course by the whole fleet. In addition, it should largely curtail encounters between friendly forces. On very dark nights or in thick weather, it will be necessary for screening and counter attacking units to be stationed outside visibility distance from the main body and each other, so that adequate warning of impending attack may be received.

STATIONING OF 8-IN. CRUISERS AT NIGHT
114.
The employment of 8-in. cruisers at night is a difficult problem. They are important ships whose armament is not specially suited for dealing with attack by light craft at night, and they are large and unhandy targets vulnerable to both gun and torpedo. If sufficient screening forces are available without them, the 8-in. cruisers should normally be stationed in the line of heavy ships. If, however, the fleet is short of screening forces, the 8-in. cruisers may be stationed in pairs on the quarters of the battlefleet whence they can generally move out to counter-attack without the necessity for large alterations of course.

POSITION OF COUNTER-ATTACKING UNITS
115.
In order to make full use of available offensive power, a counter-attacking unit should not normally consist of less than a division of destroyers; the number of units should not be increased by the employment of sub-divisions. It is better to close in the whole screen than weaken these units. If a whole flotilla is available to occupy one position it should take up Destroyer Cruising Order No. 7, as the gap between the two divisions facilitates manoeuvre and counter-attack by the rear division. However, to ensure the location and destruction of submarines and M.T.B.'s lying stopped in the path of the fleet, it may also be necessary to station destroyers singly between the advanced units of the outer screen. These destroyers should not be more than 1,500 yards apart, except on bright moonlight nights.

ACTION WHEN AN OUTER SCREEN AND COUNTER-ATTACKING FORCES ARE EMPLOYED
116. Outer screening vessels.
They should report, illuminate and attack the enemy as he goes by. Single cruisers on the outer screen should not follow the enemy in ; but if a position on this screen is occupied by two cruisers it is permissible for one of them to follow the enem, due considerations being given to the strength and position of the counter-attacking forces.

117. Counter-attacking forces. They should proceed at once to attack enemy vessels breaking through the screen in the vicinity, and should continue to engage them until they are destroyed or are no longer a menace to the capital ships. Counter-attacking forces remote from the direction in which the enemy had broken through must use their judgement to join in the attack.

ACTION WHEN A SINGLE SCREEN IS EMPLOYED
118.
When a single screen only is operating, it must combine the duties of warning and counter-attack. In these circumstance, screening units in the vicinity in which the enemy breaks through should follow and endeavour to destroy him. Screening vessels on a single screen, which occupy positions adjacent to units engaging an enemy, must use their judgement whether to join in repelling the attack ; other units on the screen should preserve their course. On a single screen, a pair of 6-in. cruisers forms a unit of great strength, particularly if the second cruiser is stationed about a mile astern of the first and takes independent action against any attacking formations illuminated by the first.

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PROCEDURE WHEN MERCHANT AND FISHING VESSELS ARE MET AT SEA

ACTION WHEN CRUISING WITH THE FLEET
122.
It is most important that merchant and fishing vessels met at sea are not allowed to sight and report the main force. They should be ordered to proceed clear of the path of the fleet, but should not normally be boarded. If available, destroyers should be attached to the advanced cruiser units for dealing with merchant vessels. If A/S air patrol aircraft or cruisers of the extended screen sight large numbers of fishing vessels, which cannot be diverted in time, a V/S report should be made to Admiral so that the main force can avoid them. If contact with enemy forces is anticipated, any suspicious vessel believed to have used W/T for reporting purposes, should be sunk ; a destroyer should be detailed to save the crew. Searchlights should not be used for the examination of merchant and fishing vessels when the fleet is cruising at night.

ACTION BY DETACHED SHIPS OR UNITS ON PATROL
123.
When a cruiser (or other type of vessel) is operating independently of the fleet and requires to examine a strange vessel, the customary signal to order her to heave to is shot across her bows. If the vessel is suspected of being hostile and armed, the following procedure should be carried out:-

(a)After the vessel has stopped the cruiser whilst keeping end-on should close to a position about a mile ahead of her, to minimise the danger of torpedo fire.
(b)If it is decided to board, a boat should be lowered and the vessel ordered to close it.
(c)The cruiser should not remain stopped in waters where submarines may be operating, but should steam away as soon as the boat is in the water.
(d)The boat should not be recovered near the position where boarding has taken place, as a submarine in the vicinity will realise the cruiser may return for this purpose.
(e)If the weather prevents the merchant ship towing the boat to a suitable recovery position (e.g., about five miles away), the boat should be abandoned and her crew and the boarding party recovered from the merchant ship later, or the merchant ship ordered to land the crew at the nearest friendly port.
(f)As soon as possible the Captain should be warned that his ship will be sunk if heard using W/T.
(g)If boarding is impossible, the vessel should be ordered to take station astern.
(h)If examining a vessel a night, a searchlight should be used as little as possible. It will usually be preferable to defer boarding until daylight.

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DEGREES OF READINESS FOR ACTION

GENERAL
126.
The degree of readiness to be assumed must meet the following requirements:-

(a) All hostile aircraft, surface ships and submarines coming within visibility distance must be sighted and reported.
(b) All the above coming within range must be engaged immediately.

Commanding Officers are responsible that the requisite degree of readiness is assumed to meet these requirements, subject to any orders that may be given by the Senior Officer. Whatever part of the armament is manned, an enemy sighted at night or in low visibility will not be engaged immediately unless the personnel is kept thoroughly alert by exercising the armament frequently in following the director, or changing "look-out bearings."

127. The degree of anti-ship and antiaircraft readiness which may be assumed are as follows, and ships should be so organised:-

(a) Anti-ship armament-Low angle, torpedo and depth charge.

1st degree of L.A. Readiness  . . Complete readiness for action against surface craft and submarines
2nd degree of L.A. Readiness  . . "Stand by" complete readiness for action against surface craft and submarines.
3rd degree of L.A. Readiness  . . Action against surface craft and submarines based on a two-watch organisation.
4th degree of L.A. Readiness  . . Anti-ship armament cleared away but hands not closed up. Antisubmarine lookouts stationed, depth charge gear and one gun manned each side.

(b) Anti-ship armament-Low angle, torpedo and depth charge.

1st degree of AA readiness  . . Complete readiness for action against aircraft.
2nd degree of AA readiness  . . "Stand by" complete readiness for action against aircraft.
3rd degree of AA readiness  . . Action against aircraft based on a two-watch organisation.
4th degree of AA readiness  . . Action against aircraft based on a four-watch organisation.

FIRST DEGREE OF L.A. READINESS, FIRST DEGREE OF AA READINESS
128.

(a) These require complete readiness for action in every respect. All officers and men must be at their action stations and the ship ready to open fire immediately.
(b) These degrees of readiness will be assumed if enemy movements show PROBABILITY of the enemy being encountered at any moment.

SECOND DEGREE OF L.A. READINESS. SECOND DEGREE OF AA READINESS
129.

(a) These require that respective full action stations should be assumed but provide for some relaxation from the first degree of readiness. Limited numbers of personnel may be fallen out in turn for meals or fresh air as the circumstances permit.
(b) These degrees of readiness are to be assumed if there is a POSSIBILITY of the enemy being encountered at any moment.
(c) Proper arrangements must be made for officers and men to rest in their quarters.

130. The first and second degrees of readiness will be those normally required when the fleet is at sea both by day and night in accordance with Clauses 128 (b) and 129 (b). It is recognised that during prolonged operations these degrees of readiness will not afford the requisite amount of sleep to all personnel. To meet this the Senior Officer may, when circumstances permit, detail ships as "guard ships" with the object of providing all ships in turn with periodical spells at lower degrees of readiness. This will be applicable to the antiaircraft armament in harbour as well as at sea.

THIRD DEGREE OF L.A. READINESS. THIRD DEGREE OF AA READINESS
131.

(a) These require the manning of half the anti-ship and/or antiaircraft armament in two watches.
(b) These degrees of readiness may be assumed as follows:-

(i) Third degree of L.A. Readiness:-By day or night when contact with enemy surface forces is possible but not imminent.
(ii) Third degree of AA readiness:-By day or night when considerable threat of air attack exists over a prolonged period.

(c) These degrees of readiness may be assumed when the maintenance of the first or second degrees of readiness for prolonged periods is likely to result in loss of efficiency, and by ships on detached duty or without close support, who will unable to benefit by the presence of a "guard ship."

Note.-There will be occasions when in the third degree of AA readiness and the fourth degree of L.A. Readiness it is necessary to man fully the AA armament. Ships should be organised so that the extra personnel required for the AA armament is available from the normal L.A. crews. In ships where the armament more particularly facilitates a three-watch system of defence, it may be desirable to organise the manning of the armaments on this basis.

FOURTH DEGREE OF L.A. READINESS
132.
This degree of readiness may be assumed:-

(a) By day when the disposition of surface and/or air forces affords the necessary degree of security from surprise encounter with enemy surface forces.
(b) By ships detailed when the "guard ship" principle is in force.

FOURTH DEGREE OF AA READINESS
133.

(a)This requires half the AA armament, to be manned in four watches.
(b) This degree of readiness may be assumed in harbour or when in the fourth degree of L.A. Readiness at sea and when there is no more than a remote possibility of air attack ; or by ships detailed when the "guard ship" principle is in force.

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DARKENING SHIP

GENERAL
135.
When at sea, ships are always to be darkened by dusk. Particular attention should be paid to vertical darkening.

GAS WATCH

136. Anti-gas precautions are to be taken when in the vicinity of enemy ships or within striking distance of enemy aircraft. (See Handbook of Chemical Warfare : C.B.3021.)

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END OF TRANSCRIPTION