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Cincpac File No. Pac-F3-Sn A2-11 (4)/A16-3 Serial 02883 UNITED STATES PACIFIC FLEET AND PACIFIC OCEAN AREAS HEADQUARTERS OF THE COMMANDER IN CHIEF   23 November 1943 CONFIDENTIAL PACIFIC FLEET TACTICAL BULLETIN 3TB-43 From: Commander in Chief, U. S. Pacific Fleet. To: PACIFIC FLEET.   SUBJECT:     Antisubmarine Screens.   References: (a) (b) (c) (d) (e) F.T.P. 188, Chapter X, Sections 60 and 61. C.S.P. 1846. F.T.P. 212. PAC-10. F.T.P. 215.   Enclosure: (A) Proposed revision of reference (a).      1.      When Pacific Fleet Tactical Bulletin 3TB-43 is made effective by dispatch, Pacific Fleet Tactical Bulletin No. 2-41 is cancelled. Reference (a) is not effective in the Pacific Fleet until further orders.      2.      This revision is consonant with information contained in references (b) to (e) and is intended to supplement them. C. W. NIMITZ   DISTRIBUTION: (13N-43)    LIST II. P, SP, MC, NTS, X, Y. Z. EN1, 3, 4, 28, NA11-54, NC3, NB18, 49, ND11-15, NY8-10, USNLO. Special:   Additional copies as necessary   to holders of PAG 10.   P. V. Mercer, Flag Secretary.

CONFIDENTIAL PROPOSED REVISIONS OF SECTIONS 60 AND 61, F.T.P. 188 SECTION 60. SURFACE ANTISUBMARINE SCREENS 1000.  Antisubmarine screens are formed for the purpose of preventing submarines from gaining a position either on the surface or submerged from which they can attack the ships being screened. This can best be accomplished by detecting, attacking, and destroying any submarine attempting to gain such an attack position.        In large forces, one, two, or three screens may be employed depending on the fleet disposition and the number of screening ships available. In small forces one screen is normally used.     There are three classes of surface antisubmarine screens, namely:   1.   The Inner Antisubmarine Screen, a close screen around a single ship or a formation of ships for the purpose of destroying a submarine approaching the screened force, or denial to that submarine of an effective torpedo firing position by: (a) the creation of wake and sound interference for the submarine ; (b) use of sound equipment and radar to detect the approach of the submarine and by tracking and attacking the detected submarine while the screened force alters course away from the dangerous waters; (c) the prevention of the use of periscope in the attack.   2. The Intermediate Antisubmarine Screen, a more distant screen formed around a formation or several formations of ships that constitute a part of a fleet disposition, for the purpose of rendering more difficult successful submarine attack upon the screened force by, (a) the prevention of use of periscope during the middle phases of submarine approach, (b) the creation of wake and sound interference for the submarine, (c) detection and tracking of submarine by sound or radar and then attacking with all available weapons. When used it is normally in addition to the Inner Antisubmarine Screen.   3. The Outer Antisubmarine Screen, a distant sound screen covering a front in the direction of advance of the formation or disposition screened. Its primary task is the detection of a submarine by sound and/or radar and the destruction of the submarine or the denial to the submarine of an effective torpedo firing position.   1001. Of these three screens the Inner Antisubmarine Screen is the most essential. The Outer Antisubmarine Screen is second in importance and will be used when the sound conditions and the number of screening vessels available, after assignment of the requisite number of Inner Antisubmarine Screen, are sufficient to render this Outer Screen effective. The Intermediate Antisubmarine Screen will be employed whenever the situation warrants and there is an excess of screening vessels over the number required for the Inner and Outer Antisubmarine Screens and Sound Screen Supports.   1002. The form of the Inner Antisubmarine Screen is dependent upon the number of ships to be screened and the number of screening ships available. C.S.P. 1846 provides illustrations and descriptions of typical numbered Inner Antisubmarine Screens for both good and poor sound conditions. Since all situations and circumstances cannot be foreseen, the Officer in Tactical Command will, when necessary, alter the forms of these types of Screens or provide new forms to meet existing conditions. Normally the O.T.C. will delegate this authority to the destroyer screen commander because of that commanders more intimate knowledge of sound conditions existing and of the respective capabilities of his ships.         It should be noted that stations on some diagrams in C.S.P. 1846 are designated by letters instead of numbers. For purposes of signalling, these stations should be considered as numbered stations in accordance with the usual plan (odd numbers in center, and to the right, even numbers to the left). —1—

1003.  The form of the Intermediate Antisubmarine Screen is not prescribed except in certain fleet cruising dispositions, where ships of the Intermediate Antisubmarine Screen are assigned stations. The General Signal Book provides signals for forming a single or double line screen on a straight line, on a bent line or on the arc of a circle. Any one of these screening formations may be used by the Intermediate Antisubmarine Screen. Furthermore, a Commander may, in special instructions, prescribe special formations for Intermediate Antisubmranie Screens, designating each by a number. The General Signal Book provides signals for forming these specially numbered Intermediate Antisubmarine Screens.   1004.  The form of the Outer Antisubmarine Screen must be such as to permit effective use of supersonic equipment for detection, tracking and attack of submarines. It is formed in advance of the ships screened in such a manner and to such extent practicable as to cover with the number of ships available all probable submarine approach sectors and to avoid mutual sonic and tactical interferences. The distance between ships of the screen should not exceed IVa times effective sound range unless a different distance is prescribed which for compelling reason disregards existing sound conditions. With the spherical projector the speed of the Outer Antisubmarine Screen should not exceed fifteen (15) knots. With the streamlined projector the effective speed will be limited to about twenty-two (22) knots. The Screen should be stationed in advance of the ships screened, at a distance which will permit completion of depth charge attacks before the submarine can close to effective torpedo firing range.   1005.  A Commander may, in special instructions, prescribe special formations for the Outer Antisubmarine Screen, designating each by number. The General Signal Book provides signals for forming these specially numbered Outer Antisubmarine Screens.   1006.  The Outer Antisubmarine Screen may be reenforced by a line of supports stationed singly about one mile in its rear, designated as Sound Screen Supports. When used the strength of these supports is one-third to one-fourth the strength of the Outer Antisubmarine Screen. The Sound Screen Supports will attack located submarines or replace units of the Sound Screen which have left their screening stations to attack. The decision as to which action the Supports will take under the circumstances will rest with the Senior Officer of the vessels of the Screen which are in actual contact with the submarine. The Outer Screen Commander, giving due consideration to the existing sound conditions and the width of the front to be covered, will decide whether it will be more advantageous to utilize all available vessels in the Sound Screen or to divide his force into a Sound Screen plus Sound Screen Supports.   SECTION 61.  GENERAL MANEUVER INSTRUCTIONS FOR ANTISUBMARINE SCREEN   1007.  PATROLLING STATIONS. — Ships of the Intermediate Antisubmarine Screen and ships of the Inner Antisubmarine Screen, designated in the diagrams to patrol, will normally patrol their stations whether or not the ships screened are zigzagging, except that when on screening stations during periods of low visibility, they will normally not patrol, but will conform to courses steered by the ships screened. The main purpose of patrol by Inner and Intermediate Antisubmarine Screens is to create interference for the sound approach of the submarine. On moonlight and starlight nights, when the visibility is such as to warrant the vessels of the Inner Antisubmarine Screen patrolling their stations, they should do so. The Screen Commander shall determine whether or not the Screen will patrol stations, and his decision must be based on fuel expenditures as well as conditions mentioned above.   1008.  BEARING OF SCREENING STATIONS FROM SHIPS SCREENED. — The stations of ships shown in the diagrams for typical Inner Antisubmarine Screens are determined with relation to the force screened when that force is on its base   —2—

course. In forming, the screening ships will take station by using the relative bearing from the nearest ship of the force screened. For purposes of station keeping, this bearing should be converted into a true bearing from the nearest ship of the force screened. For compound formations and simple column formation, stations are arranged to give adequate protection to the formation while zigzagging and during temporary changes of course, if the approximate true bearing of the station from the nearest ship of the force screened is preserved by the screening ship. With single ships screened by less than four screening ships, the necessity for protecting the most likely area of attack demands that the approximate relative position of these stations be preserved at all times, in order to prevent the more probable avenues of submarine approach from being uncovered during zigzagging or change of course.   1009.  Ships assigned to the stations of the Intermediate Antisubmarine Screen in a fleet disposition will patrol their stations in accordance with Article 1007 and maintain stations in relation to the fleet axis, unless ordered by the Officer in Tactical Command to maintain station in relation to the fleet course.   1010.  REORIENTATION OF THE OUTER ANTISUBMARINE SCREEN, DUE TO CHANGES IN FLEET COURSE.   (a)  Ships assigned to the Outer Antisubmarine Screen (Sound Screen) in a fleet disposition, or in a formation, maintain station on their own formation guide. Normally the Outer Antisubmarine Screen should be oriented with respect to the* fleet course. Due to the length of time required to reorient the Sound Screen, such reorientation normally should not be attempted for a temporary change in fleet course, but is required for a change of course of considerable duration. The Officer in Tactical Command shall direct changes in orientation of the Sound Screen.   (b) In a fleet disposition, the Outer Antisubmarine Screen is so far from the fleet center that an appreciable change in orientation requires a considerable movement of the screen. If effective screening is to be maintained during the process of reorientation, a considerable length of time is required. However, without materially reducing the protection afforded units near the fleet center, the process of reorientation may be commenced in advance of the change in fleet course.   (c) The details of effecting the reorientation of the Outer Antisubmarine Screen shall be left to the discretion of the Screen Commander. In order that the Screen Commander may reorient the Sound Screen in such manner as to most effectively screen the disposition, the Officer in Tactical Command should inform the Screen Commander at least one hour in advance of changes of fleet course, including designation of the new fleet course.   (d) Certain thumb rules in connection with reorienting the Outer Antisubmarine Screens of Fleet Cruising Dispositions to cover changes in fleet course, are as follows:   (1)  So long as the fleet speed is not in excess of nine tenths of the effective screening speed (15 knots with spherical projectors, 22 knots with streamlined projectors), changes in orientation of ten degrees or less can be effected by uniform angular rotation of Sound Screen. If practicable, such rotation should commence about a half hour prior to the change in fleet course.   (2) Extending the Sound Screen by adding four ships to the end toward the direction of the change of course will cover a change of course of approximately twenty degrees.   (3) Such extensions of the Sound Screen should be effected by using Sound Screen Supports, if available, or by shifting screening vessels from one end of the screen to the other. Give due consideration to fuel expenditures.   —3—

(4) Dependent on the amount of the course change and whether Sound Screen Supports are available, the process of reorientation may consist of one of, or any combination of the following: (a)  Uniform angular rotation of the screen. (b) Extension of the screen by use of the Sound Screen Supports. (c) Shifting of screening units from one end of the Screen to the other end.   1011.  THE SCREENING INTERVAL of the Intermediate and Outer Antisubmarine Screen is normally prescribed diagramatically for each fleet cruising disposition. When not so prescribed these screening intervals will be ordered by signal.   1012.  ZIGZAGGING. — Ships of the Inner and Intermediate Antisubmarine Screen will conform to the zigzag plan being executed by the force screened, whether or not ships of the Screen are patrolling their stations, and will keep clear of ships of the force screened at all times. Ships of the Outer Antisubmarine Screen will conform in general to the zigzag plan being executed by the force screened, but will use such modifications of this zigzag plan as are necessary to avoid interference with effective sound search operations.   1013. Ships of the Inner Antisubmarine Screen, which generally conform to the zigzagging of the force screened, will preserve the approximate true bearing of their stations (center of patrol area for patrolling vessels) from the nearest ship of the force screened, except in the case of screening a single ship with less than 4 screening ships, when relative bearings are to be maintained.   1014. SIGHTING OR DETECTING SUBMARINE BY A SHIP OF THE ANTISUBMARINE SCREEN. Make the appropriate submarine emergency signal and then follow detailed procedure outlined in F. T. P. 219 (Par. 2302 etc.).   1015. APPROACH AND CONTACT DISPOSITIONS. — When an approach or contact disposition is formed from a cruising disposition in which Antisubmarine Screens are employed, the Screens will, unless otherwise ordered, proceed as directed in this article. Inner Antisubmarine Screens of the battle line, aircraft carriers and train continue to operate as Inner Antisubmarine Screens. All other vessels employed as Antisubmarine Screens proceed to stations for disposition ordered.   1016. DEPLOYMENT. — When deployment is ordered from a cruising, approach or contact disposition in which Antisubmarine Screens are employed, the Screens will, unless otherwise ordered, join the task forces to which they are assigned for battle.   1017. TO FORM AN ANTISUBMARINE SCREEN. — SIGNALS REQUIRED: (a) Appropriate signal to form type of screen desired. (TACK numerals may be added to identify the plan). (b) Appropriate signal for forming single or double line screen on arc or on straight or broken line. NOTE: For the Inner Antisubmarine Screens in these instructions the stations to be occupied are indicated in diagrams and tables accompanying each diagram.   MOVEMENTS REQUIRED: Ships of screening unit(s) take flank speed and proceed by most direct route to screening station keeping clear of heavy ships. For Inner Antisubmarine Screens in these instructions, stations will be occupied in accordance with the table accompanying each diagram, depending on the number of ships available. —4—

1018.  A DISABLED SINGLE SHIP lying to or proceeding at a speed of five knots or less should be screened against enemy submarines as follows: (a)  With only one screening vessel available — That screening vessel will circle the disabled vessel at about 2,000 yards distance using best sound speed if sound conditions warrant, or at best practicable speed under poor sound conditions. (b) With two or three screening ships available, they will circle the disabled vessel in a clockwise direction equally spaced at a distance of about 3,000 yards from it, at fifteen knots speed (with spherical projectors) or twenty knots speed (streamlined or no projectors). (c) If there are more than 3 screening vessels available all will immediately join the circle prescribed in (b) and so continue until the 0. T. C. directs another specific disposition for those ships in excess of three should he deem such to be expedient.                   —5—

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