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1. Consideration has been given to the installation of A/T baffles within Pearl Harbor for protection against torpedo plane attacks. It is considered that the relatively shallow depth of water limits the need for anti-torpedo nets in Pearl Harbor. In addition the congestion and the necessity for maneuvering room limit the practicability of the present type of baffles. (Comment: In other words, the shallowness of Pearl Harbor provided a natural defence against air-dropped torpedos and due to the high number of ships in the harbor it would be impractical to have a system that had to be dismantled every time one ship needed to move, let alone all of them.)
2. Certain limitations and considerations are advised to be borne in mind in planning the installation of anti-torpedo baffles within harbors, among which the following may be considered:
3. As a matter of interest the successful attacks at Taranto were made at very low launching heights at reported ranges by the individual aviators of 400 to 1300 yards from the battleships, but the depths of water in which the torpedoes were launched were between 14 and 15 fathoms(Comment: roughly 85-90 feet). The attacks were made in the face of intensive and apparently erratic anti-aircraft fire. The eastern shore line of the anchorage and moorings were protected by numerous balloon barrages, but there was no trawler borne balloon barrage to the west. The torpedoes were apparently dropped inside of the nets, probably A/T nets.
4. It is considered that certain large bays and harbors, where a fleet or large force of heavy ships may be anchored and exposed with a large body of water on an entire flank, should have that flank protected by a series of baffles if the water is deep enough for launching torpedoes. The main fleet anchorage at Scapa Flow, for instance, has an A/T net extending slightly to the north of a line between Calf of Flotta and Cava Island protecting the main fleet anchorage. The depth of water where this net is laid is approximately 17 fathoms. On the other hand constricted harbors, in which practically all available space is taken up by anchorages, and which is relatively deep probably must depend upon other defense measures. It might be possible and practicable to provide in some places, which are not protected by relatively shallow water, anti-torpedo baffles practically surrounding a limited number of berths or large ships, such as battleships or carriers. An extreme example of this is furnished at the present time by the French at Dakar, where double nets surround the Richelieu; she is placed similarly as in a dry dock, and evidently would have to open a section of the net to be hauled clear. The depth of water at Dakar, however, is very shallow.
5. The present A/T nets are very expensive extremely heavy, their heavy anchors and moorings take up about 200 yards (Comment: 600 feet, which would have put the anchors of the nets past the middle of the channel) space perpendicular to the line of the net, take a long time to lay, and are designed to stand up under heavy weather conditions. There is apparently a great need for the development of a light efficient torpedo net which could be laid temporarily and quickly within protected harbors and which can be readily removed. It is hoped that some such net can be developed in the near future.
6. Recommendations and comments of the Commander-in-Chief are especially desired.
(s) H. R. Stark.
H. R. STARK.