User Guide

Periscopes were useless at night. However, in clear weather it was advantageous
when running on the surface to post a “high periscope watch” in other words, to
have a lookout man a raised periscope. The increased “height of eye” provided a
significant increase in the distance to the horizon and the range at which a target
could be detected.
Vision is important in searching for targets. It was customary when on the sur-
face to post three lookouts on the bridge in addition to the Officer of the Deck
(OOD) and the Junior OOD. Vision capabilities of individuals vary considerably,
and that is particularly true of “night” vision. Submarines “rigged for red” in the
conning tower and elsewhere below decks as darkness approached so that the
night vision of those going to the bridge would not be adversely affected by the
normal white lighting. In addition ambient atmospheric conditions, of course,
affect vision performance.
Number of Torpedoes Available
There were normally 14 torpedoes carried in the forward torpedo room at the
start of a patrol; 6 in the tubes and 8 in the racks. In the after torpedo room, 10
torpedoes were carried; 4 in the tubes and 6 in the racks. As a patrol progressed
the numbers decreased as torpedoes were expended. Most attacks were made
using torpedoes from the forward room. Although stern shots were possible to
augment the number fired from the bow, and vice versa, the gyro angles of torpe-
does fired from the secondary set of tubes would usually be large. In my opinion
that decreased their accuracy. If it is necessary to fire torpedoes from the stern
tubes it was better to plan the attack with this in mind
Torpedoes could not normally be transferred between torpedo rooms at sea, although
it was done on the surface on at least one occasion. I would not recommend it.
Single Submarine or Wolfpack Attack
A torpedo attack consists of two phases, the approach to attain firing position, and
the firing of torpedoes. Approach maneuvers depend largely upon the disposition
of the target(s) relative to own ship.
Coordinated operation of groups of submarines in wolfpacks has a number of
advantages including a large increase in the area being searched, the ability to
conduct simultaneous attacks, principally on convoys, from several directions,
and saturation of escort defenses. Coordination was achieved through adherence
to a prescribed set of tactics, codes, and inter-communications by means of voice
radio. Many wolfpack operations were conducted by Pacific Fleet submarine in
the period between October 1943 and Mid 1945.
When a coordinated attack is delivered each member of the wolfpack conducts its
attack on a designated target, or target of opportunity, in essentially the same
manner as a single submarine.
SILENT
HUNTER
72 APPENDIX B — TACTICS
It was also critical that the position of threatening escorts be continually moni-
tored. When making a night surface approach from ahead of the convoy, the
range to nearest escort was of particularly concern because the closing speed was
approximately the sum of own ship’s and escort’s speeds. Unlike an automobile, a
submarine cannot stop or turn on a dime if necessary to avoid collision.
Submarine Submerged Speed and Endurance
At target speeds of 15 knots and greater submerged submarines often had diffi-
culty getting into attack position because of low speed and limited battery
capacity. In such circumstances it was often necessary to surface and do an “end-
around” at full speed. This could take the better part of a day depending upon
target speed. Upon getting ahead of the convoy or target the submarine could
submerge for another attack if position was gained during daylight, or await dark-
ness and deliver a night surface attack.
Sea Conditions
Waves and swells do not always travel in the same direction. Submarine depth
control at periscope depth is difficult in heavy seas, particularly when running
into them or when they come up from astern. Use of the SJ surface search radar
during the first few years of the war was hindered when submerged in heavy seas
because the antenna was mounted atop the periscope shears, requiring the sub-
marine to run at relatively shallow depths (e.g. 40 to 45 feet). Near the end of the
war an extendible mast was installed so that the antenna could be raised and low-
ered much like a periscope.
The speed of submarines on the surface with a full fuel load, as during the early
days of a patrol, is limited when running into heavy seas by “green water” (waves)
coming over the bridge and often up to the lookouts in the periscope shears. It is
sometimes necessary under such conditions to slow to as little as five knots.
Submarines are much less affected by waves and swells when submerged than
ships on the surface. At a keel depth of 100 feet they are relatively stable.
Unfortunately, below periscope depth (about 68 feet) they are totally dependent
upon passive (listening) sonar for search and target information.
Visibility Conditions
Submarines have a much smaller silhouette than any surface ship. Thus, they can
often approach within one to five miles or less of a target or escort at night with-
out being detected, depending upon moonlight, starlight, and clarity of the air.
Because the Japanese did not normally have surface search radar, visibility condi-
tions were important in attaining attack position for night surface attacks. The
Japanese did have 20 power binoculars with excellent light gathering capability
for night vision, but that did not seem to affect us significantly.
SILENT
HUNTER
71 APPENDIX B — TACTICS