cadre (n.)

"permanently organized framework of a military unit" (the officers, etc., as opposed to the rank-and-file), 1851; earlier "framework, scheme" (1830); from French cadre, literally "a frame of a picture" (16c.), so, "a detachment forming the skeleton of a regiment," from Italian quadro, from Latin quadrum "a square," which related to quattuor "four" (from PIE root *kwetwer- "four"). The communist sense "group or cell of workers trained to promote the interests of the Party" is from 1930.