Memorandum on Submarine Chaser Operations from Captain Richard H. Leigh, Operations Section, U.S. Naval Forces Operating in European Waters
S E C R E T U. S. S. LEONIDAS
U. S. NAVAL BASE NO. 25.
10 June 1918.
OPERATIONS OF U. S. SUBMARINE CHASERS
1. MISSION: The object of the Barrage is to prevent the passing of the enemy’s submarines through the Straits of Otranto and thereby preventing the destruction of Allied and Neutral Shipping by submarines based at enemy ports in the Adriatic Sea. The destruction of all submarines not known to be in this area by orders issued by the Barrage Force Commander must be the immediate object of all vessels.
2. The Barrage consists of a screen of destroyers for protection against raids by surface craft – trawlers fitted with listening devices – motor boats – drifters – supporting destroyers fitted with kite balloons, air craft, listening stations on shore and submarine chasers. The exact disposition of the forces will vary. It is therefore necessary that each time before going on station, that Commanding Officers of Chasers shall visit the operation room and verify the latest disposition of forces in order that no interference shall be possible. Exactness as to listening periods is absolutely necessary.
3. The air must be kept free at all times, it is therefore necessary that no message be repeated. Every message may be of vital interest to you and all must be recorded and decoded. Under no circumstances will an operator listen on any except the prescribed wave length. Press news will be furnished upon the return of the vessel to the Base.
4. All clocks and watches upon going on patrol will be set to G.M.T., and all times, written orders and reports pertaining to the Barrage are to be expressed in G.M.T. Time signal is made daily at 0600 by Otranto. This is not for use in correcting Chronometer Rates.
5. All bearings and courses shall be true except that sound bearings will be magnetic.
6. Formation will be maintained when proceeding from the base through swept channel. Immediately after leaving the swept channel each vessel will proceed on a course direct to her station, stopping and listening with the M. B. tube or S.C.C. tube for three minutes every half hour. This listening period will conform to the silent periods prescribed by the Commanding Officer of the Barrage. If sound contact is made with a submarine the hunt will begin at once, using the same signals as elsewhere assigned.
7. Arrived on station and having relieved the vessel already on duty, each chaser will maintain a listening watch during the day time with the S.C.C. tube, the M. B. tube or the “K” tube as directed, at night with the “K” tube, checking frequently with S.C. and M.B. tubes. When speed cones are down all vessels will be listening and on hearing a submarine two drums will be hoisted vertically at the gaff or radio yardarm, the arrow will be set for the direction of the sound and shown to the adjoining vessels. Attack, hoist cross and speed cone – let go first depth charges on hauling down cross and blast of whistle. When going ahead the speed cone will be hoisted. Lowered when stopped and reversed when backing.
8. At night vessels will not show lights except when a vessel of the Allied forces comes near or when contact with a submarine is made. These lights will be as follows:-
GOING AHEAD:- Dimmed running lights burning and white truck light shown at intervals.
STOPPED:- Red truck light flashed and side lights on.
ATTACK:- All lights on and arrow revolving.
LET GO DEPTH CHARGES:- Out truck lights and one long blast on whistle. Other charges will be let go according to prearranged plan.
9. Units will sail at 0400 and will return on the fourth day as soon as relieved. This will make three days on station.
10. On return to American Bay, Corfu, Commanding Officers will immediately fill up with gasoline, lubricating oil, water and in all respects prepare their vessels for sea. Officers from the LEONIDAS will go on board the vessels to inspect and start work on any damaged parts. It will not be necessary for the vessels themselves to make any request for repairs other than verbal requests to the officers from the LEONIDAS. Details of these requirements will be set forth in another order of the Base Doctrine.
11. SPEED:- Vessels proceeding to and returning from the Barrage may proceed at a speed of 12 knots.
12. For running patrol unless otherwise ordered the speed will be 10 knots. When in pursuit full speed of course will be used.
13. The utmost economy in gasoline and lubricating oil consumption is vital and Commanding Officers will give their personal attention to this matter. No chaser will go on the Barrage more than 200 gallons short of full capacity of gasoline.
14. Depth Charges will be carried at safety until in pursuit, when they will be set at 150 feet.
15. The charges will be dropped according to the plan. The pattern may be changed by the Detachment Commander but in all one principle should obtain and that is:- “When it is worth dropping depth charges at all, it is worth dropping a lot.” When on station the depth charge projector will always be manned, also 3 inch gun. The signalmen will understand how to operate the machine guns.
16. The 3 inch guns will not be loaded but ammunition kept at hand for instant use.
17. SIGNALS This subject is fully covered in another order but chasers are to exercise signalling between one another by visual as much as possible in order to obtain practice.
18. DRILLS:- Tactical drills will be held in the Bay during rest periods until everybody is thoroughly familiar with the tactics which are used against submarines.
19. On station loading and aiming drills will be held also aiming drills with the .30 cal. rifles.
20. POSITION on PATROL:- All chasers on Barrage are to keep a slip in the pilot house on which is to be written the position which it is expected the ship will occupy one half hour later and the wireless operator is to be notified of this position. The position will be from the Squared Chart also by Latitude and Longitude. Thus at 1800 the predicted position at 1830 will be recorded on the pad by the predicted squares and by Latitude and Longitude.
21. These positions are to be used in making reports of surface craft or submarines in accordance with M.A.P. 3.
22. That is in case of “Alert” messages in Latitude and Longitude, and in case of the subsequent enemy report by squared chart.
23. The “Allo” form of “Alert” signal is not to be used by any vessels on the Barrage. Reports of Submarine being heard, seen or attacked are coded by means of the “Emergency Table” or by groups from the phrases section of the code. The other code words for use with “Alert” messages are to be used as laid down in the instructions.
24. AIR CRAFT RAID:- For the present vessels in port will get underway in the day time and scatter to the Eastward, at night will remain at their moorings – darkened. Guns will be manned but fire will not be opened except by order of the Senior Officer Present. Absolute silence will be maintained so that orders may be given by word of mouth.
25. On Barrage fire will be opened by the riflemen and guns crews at the discretion of the Commanding Officers. Rifles and Colt’s guns should be aimed well ahead of the air craft and sliding leaves set well over in the direction the target is travelling.
26. SURFACE CRAFT ATTACK:- In case of an attempted raid by surface craft. Vessels in the Eastern part of the line will proceed to the Southward and take shelter in the bight close to the Albanian Coast. Continue to the Southward in this bight for it is doubtful if any enemy surface craft would enter far into a trap of this nature.
27. Vessels in the middle of the line proceed to the southward and take shelter close in to Fano Island where enemy surface craft are not likely to risk the mine fields.
28. Vessels on the western end of the line will proceed to the southward closing on the Italian coast and taking shelter at Cape Sta. Maria di Leuca.
29. Vessels should avoid closing more than necessary to reach the same point. Do not try to herd together.
30. The first warning of surface craft may be obtained by your own listening apparatus and there is danger of confusing a submarine running on the surface with a surface raid. Surface raiders will probably come from the northward and will be very fast vessels. In case a raider has passed through the destroyer patrol without being reported remember thatyour first duty is to report it and run away. It will never pay to try to engage enemy surface craft.
31. STRESS of WEATHER:- If ordered to leave station because of bad weather vessels will take shelter as follows:-
Vessels at the Eastern end of the line will take shelter at Port Palermo.
Vessels in the middle will take shelter near Farno Island Northward or Southward so as to get a lee.
Vessels on the Western end will use Otranto or Port Castro, the former for southerly the later for northerly winds.
32. HUNT FORMATION:- The vessel first hearing the submarine hoists the proper signal (two drums) and notifies the other vessels of the Hunting Unit by wireless telephone, giving bearing then reports by wireless telegraph as provided in the “Emergency Table” or by the Code. She then hoists the speed cone and heads for the point where the submarine was heard. All vessels of the Unit [words obliterated] flag for hunting. Plotting begins at once. The other vessels of the Unit head for the submarine’s position and close on the vessel which first heard the submarine, trying to keep on the beam of directing vessel. When the first vessel stops the other vessels will also stop regardless of their positions. The ideal position is for the middle vessel to be in the wake of and on the course of the submarine, the wing vessels to be equal to the distance of the submarine ahead. This gives 43º angles which are the best for plotting. After the first stop wing vessels may be given an opportunity to obtain this position by the centre vessels going ahead slow if she is in sound contact or if she is not in contact then by the hearing vessel going slower. The distance away of the second will of course determine to a large extent the advisability of getting into formation. The first thing to do is to get close with at least one vessel.
33. When hunt has started listening on time signal ceases automatically; stops are made by the directing vessel.
34. Vessels will close automatically to 100 yards. 100 yards distance is the basis for all patterns which are used in the attack. From this formation the pattern agreed upon is laid out and all vessels will hurry to this position (line abeam 100 yds. distance) in case the attack is ordered.
35. Immediately after the attack all vessels will stop and listen unless there are visable signs of the success of the attack. At this time all depth charges which have not been expended should be whipped up into place, the depth charge projector reloaded and the 3 inch gun manned ready to attack at once in case the submarine comes to the surface.
36. At night when in pursuit vessels will burn dimmed navigation and stern lights.
37. Suggestions are invited.
38. Reports of operations will always show whether or not there was any interference from our own or Allied war or merchant vessels. At what distance and time and whether or not the sound interference was from main or auxiliary machinery.
R. H. LEIGH