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Serial 055730
Washington, June 13, 1941,

From: The Chief of Naval Operations
To: The Commandant, First Naval District Northeast Coast
The Commandant, Third Naval District Northeast Coast
The Commandant, Fourth Naval District East Northeast Coast
The Commandant, Fifth Naval District East Northeast Coast
The Commandant, Sixth Naval District Southeast Coast
The Commandant, Seventh Naval District Florida Coast
The Commandant, Eighth Naval District Southern Coast
The Commandant, Ninth Naval District Midwest/Great Lakes
The Commandant, Tenth Naval District Carribean Sea
The Commandant, Eleventh Naval District Southwest Coast
The Commandant, Twelfth Naval District North Californian Coast
The Commandant, Thirteenth Naval District Northwest Coast
The Commandant, Fourteenth Naval District Hawaii
The Commandant, Fifteenth Naval District Panama Canal Zone
The Commandant, Sixteenth Naval District Philippine Islands
Subject:      Anti-torpedo baffles for protection against torpedo plane attacks.
Reference: a) CNO conf. ltr. Op-30C1 Serial 010230 of Feb. 17, 1941.

     1.     In reference (a) the Commandants were requested to consider the employment of and to make recommendations concerning anti-torpedo baffles especially for the protection of large and valuable units of the fleet in their respective harbors and especially at the major fleet bases. In paragraph 3 were itemized certain limitations to consider in the use of A/T baffles among which the following was stated:

"A minimum depth of water of 76 feet may be assumed necessary to successfully drop torpedoes from planes. About two hundred yards of torpedo run is necessary before the exploding device is armed, but this may be altered."

     2.     Recent developments have shown that United States and British torpedoes way be dropped from planes at heights of as much as three hundred feet, and in some cases make initial dives of considerably less than 75 feet, and make excellent runs. Hence, it may be stated that it can not be assumed that any capital ship or other valuable vessel is safe when at anchor from this type of attack if surrounded by water at a sufficient distance to permit an attack to be developed and a sufficient run to arm the torpedo.

     3.     While no minimum depth of water in which naval vessels may be anchored can arbitrarily be assumed as providing safety from torpedo plane attack, it may be assumed that depth of water will be one of the factors considered by any attacking force, and an attack launched in relatively deep water (10 fathoms or more) is much more likely. (Comment: 10 fathoms is 60 feet)

     4.     As a matter of information the torpedoes launched by the British at Taranto were, in general, in thirteen to fifteen fathoms of water, although several torpedoes may have been launched in eleven or twelve fathoms. (Comment: a fathom is six feet)


Copy to CinCpac. CinClant. CinCaf. C. O. Naval Net Depot, Tiburon. C. O. Naval Net Depot, Newport. Comdt. NavSta, Guantanamo. Comdt. NavSta, Samoa. Buord. Op-12.