The various pamphlets are prepared under direction of the chiefs of various branches of the service. Previous editions, numbered in volumes, parts and chapters, lacked series designation. In the Library of Congress each pamphlet forming a part of this manual is classified individually.
"The number of each pamphlet will consist of two parts; the basic number and subnumber. The basic numbers will be as follows: ... 20 to 30--Basic field manuals ... The subnumbers for Field manuals will be from 1 to 199."--War department Circular no. 36, April 6, 1940.