The pentakosiarch commanded a pentakosiarchy (πεντακοσιαρχία, pentakosiarchia) of 512 men, composed of two syntagmata of 256.
During the time of Alexander the Great, selection of the pentakosiarch was based on merit.
An account, for instance, described a contest of valor at Sittakene for hypaspists where six pentakosiarch and three chiliarch were selected.
On 14 December 1868,[3] a Royal Decree authorized the creation of thirty 'independent pentakosiarchies of volunteer light infantry' (αὐθύπαρκτοι πεντακοσιαρχίαι ἑλαφροῡ πεζικοῡ ἐξ ἐθελοντῶν) for the Greek Army, intended to serve as a militia.
Numbered consecutively from 1 to 30, each was in turn composed of four hecatontarchies of 150 soldiers and 10 officers and NCOs each.