[Heibges]

78) A rough sea state restricts the use of the submarine as a weapon of war:

a) as regards the underwater use of torpedoes: as soon as the underwater steering gear can no longer be controlled at periscope depth. In the case of small submarines the dividing line will be between sea No. 5 or 6, for medium and large boats, sea No. 6 or 7, approximately.

b) as regards the surface use of torpedoes: the dividing line in this case is reached in somewhat less rough conditions than apply to the underwater use of torpedoes, on account of the unfavorable influence of the rough sea on the maneuverability of the vessel on the surface.

100) Favorable Conditions for attack.

c) wind 3 to 4 and sea 2 to 3 are most favorable for making the attack because the sea then washes over the low-lying periscope, without interfering with the view of the target, while the action of the underwater steering gear is not adversely affected.