However, if the forces available are not deemed adequate, the commander either modifies the operations, or restricts them, or subdivides them into parts for performance in succession by stages.
"Sound Military Decision"
U.s. Naval War College
Vogel subdivides the class into three groups.
"The Story of the Heavens"
Robert Stawell Ball
This second method subdivides itself into two different varieties.
"A System Of Logic, Ratiocinative And Inductive (Vol. 1 of 2)"
John Stuart Mill