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Captain Thomas C. Hart, Commander, Submarine Flotilla Two, Anti-Submarine Instructions

<13 August, 1918.>


     1.   PATROL BILLETS. A Secret Memorandum giving our Submarine Patrol Lines and Areas in force will be issued from time to time. All billets are always to be assumed occupied unless definite information to the contrary is received.

     2.   NAVIGATION. See Confidential General Orders, Coast of Ireland,1 for information concerning swept channels.

          Navigation is likely to be difficult; facilities for navigation are poor, thick weather likely, and currents are strong – but to fail to keep located may mean danger from friends, as well as from grounding, and will mean inefficient patrol; a S.O.S. message cannot be of use unless you know your position. Commanding Officers, in addition to Navigators, will work navigation; much of it will be D.R. [i.e., dead reckoning] only, in which practice and experience is the most useful asset and which can offset the lack of recording logs. Study the data on currents and always include the probably set in working D.R. Currents are much affected by wind; an unexpected N.W. [i.e., northwesterly wind] is likely to be experienced off the South Coast of Ireland. If there is navigational light within easy distance, toward which there is no great danger of encountering surface patrol, run in and pick it up at night and get a departure.

          For this Service, the best astronomical observations are those of stars at morning and evening twilight;- they give an immediate and definite fix and are taken at times which will least interfere with patrol. In coming to surface for meridian altitude, remember that enemy is likely to be up for same purpose; a “near-noon” sight within 30 m. of meridian is just as good as the meridian sight, and takes less time of observation. Soundings in these waters are deep and far less a guide than those to which you are used; but in nearly all places, outside 30 fathoms is safe. Use a 50-fathom lead, with a reel.2 Use your discretion as to taking shelter in bad weather.

          During a patrol, keep a rough track chart showing all position fixes and location of any important occurrences. Submit same upon return of the patrol; the latter may be extracted from the War Diary covering the period.3 In event of encounter with enemy, submit full detail in the report. Return all copies of Sailing Orders to point of issue, for destruction, upon return.

     3.   On patrol, and at any time at sea, you have two objectives:-

          (a) Attacking enemy submarines, and

          (b) Security of own ship from attack by friends – as well as from the usual dangers of the sea.

          At all times, have uppermost in your minds exactly what you are going to do – under conditions obtaining at the time – if your vessel contacts with enemy or with friendly vessels.  Do not waste energy but be forehanded in all things pertaining to those two main issues; keep all preparations made ahead of the time, when such preparedness may be required,-lose no opportunities. Do not permit yourselves to be surprised and guard against your subordinates being surprised, or in any way excited, by your orders. BE READY.

     4.   SUBMERGING. The quick dive is of great importance. Except at night or in thick weather, in no other way are you likely to damage the enemy, and you may at any time have to do it to evade attack by friends. Keep trimmed and compensated, and retain only enough buoyancy for the work in hand.

          Submerging should be an “all hands” matter, though you cannot keep all hands continuously at stations; but arrange watches so that all preliminaries to diving will be started at the signal – your men practically get their sleep and food at their stations anyhow. Adhere to the organization and station bills for the normal number of personnel. With supernumeraries, employ them for their best instruction, but don’t thus disrupt the organization. Keep a quiet ship. Don’t have any calling of orders and reports back and forth that can be avoided; use speaking tubes and require all your subordinates to use as low voice as can be heard. Everyone yelling about, unnecessarily loud orders and reports are confusing, exciting, and beget or show inefficiency.

          Steer from below; don’t have more than four on the bridge at any time. Don’t have running or electric signal lights so disposed as to interfere with your readiness to dive. When using aerial, mast extended, keep all in readiness for a quick dive.

     5.   ON PATROL. If not definitely ordered to keep, by day, either a submerged or a surface patrol, your decision as to which to keep must be from a thorough consideration of all the elements of the problem. There are the following points:-

          (a) Enemy has the same decision to make. In narrow waters, he is probably submerged; in outlying waters, in absence of air-craft and thick surface patrol, he is more likely to be on the surface,- to widen his horizon. His periscopes are certainly superior to yours, and probably his binoculars also are.

          (b) In calm weather and good visibility, the normal method should be submerged patrol with at least two feet of periscope out, coming to surface about once an hour to examine the horizon with glasses; if rough, it is advisable to spend more time on the surface.

          (c) In outlying patrol, it is advisable to spend more time on surface:- you have the chance of intercepting a S.O.S. or other informative message, and enemy is more likely to be on surface. He is very likely to be hunting on surface during morning and evening twilight.

          (d) It’s a matter of seeing the enemy before he sees you. Remember your defective optical instruments, guess what the enemy is doing, and decide whether the advantage to be gained with your binoculars offsets your own greater visibility on surface.

          If, from intercepted S.O.S. or war warning, the presence of an enemy submarine is suspected, keep a diving patrol. At night, with fair visibility, keep a surface patrol unless you wish to try by listening. In thick weather or during very dark nights, unless you have to charge, submerge and run deep – for your chance of success is slight and you are, in such weather, in most danger from your friends. On surface patrol, all who show above bridge rail are to wear white or very light coverings. Keep away from all patrol craft, for where they are, the enemy will not show himself.

          Follow unconvoyed merchantmen within the limits of your billet,- to be on hand, and contact with an attacking enemy; but don’t be sighted, for you will be reported as an enemy and thus disorganize traffic. Do not trail a hospital ship; you risk giving enemy chance to say you were convoying her.4

          If you observe the torpedoing of a ship, close the position, as the enemy may come up to communicate with survivors. But do not close one within five miles of the coast for she probably has been mined rather than torpedoed.

          If an enemy submarine is known to be submerged in your vicinity, on the approach of a merchant vessel, you are to show yourself for the purpose of frightening her away, only when you are certain that by so doing she must alter course away from the position in which you know the enemy to be. If in doubt on this point, it is better to remain unseen and wait for your chance of attack, which, if successful, will save many ships.

          If you fail in an attack, if the enemy knows of your presence and you know a convoy is approaching the locality, come up and report the situation in Q wave, to all ships, or direct to the Convoy Escort as soon as possible.

          If the convoy passes near you, keep out of sight, submerged, and work over to its wake. An enemy having failed in submerged attack is likely to come to surface and follow with intention of attacking at night, from its quar[t]er or by getting ahead of it.

          While patrolling submerged, make full use of listening devices up to the easy endurance of the men. At such times and particularly when you have sighted an enemy, the S-C or K. tubes5 are decidedly an asset. It is expected that with them you will be able to accomplish more in keeping in touch with a submerged enemy than has thus far been done. A submerged enemy will probably hear you, but, as far as known, he is unable to get your direction. The possibilities in this development are considerable and the device may somewhat offset the deficiencies in periscopes. By listening submerged you may detect an enemy running on surface and are authorized to try.

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Subject: <Instructions Governing Anti-Submarine Patrol.>

Source   <13. C.H.J.>

Date:    <August, 1918.>

     10.  ENGINES. Unless you need the speed, never run faster than the slowest smooth speed of the engines. In good condition, the engines will wear least at 300 to 310 R.P.M. Unless you have to charge at the same time, always use both engines if you have distance to make; the wear will be less; and the boat will be in better control. Use above water exhaust except under unusual circumstances during still nights in smooth water. When an engine is stopped, always prepare it for diving, without further order.

THOS. C. HART.                    

Captain, U.S.NAVY;COMMANDER, Submarine Flotilla Two,

Source Note: D, DNA, RG 45, Entry 520, Box 315.

Footnote 1: These orders have not been found.

Footnote 2: Hart is describing a process for taking depth measurements. A 50-fathom lead is a measure with a weight on the end that can descend up to 50 fathoms before being pulled back in.

Footnote 3: For examples of submarine war diaries, see, DNA, RG 45, Entry 520, Box 1370. The boxes immediately following contain additional material on submarine operations.

Footnote 4: For the rules governing hospital ships, see: Memorandum to William S. Benson, 25 July 1918.

Footnote 5: Two types of listening devices.