Among the ancient Romans a body of soldiers consisting of three lines, the hastati , the principes , and the triarii , ranged in order of battle one behind the other, each divided into ten maniples, and the whole numbering from 4000 to 6000 men; to each legion was attached six military tribunes, who commanded in rotation, each for two months; under Marius the three lines were amalgamated, and the whole divided into ten cohorts of three maniples each; under the original arrangement the hastati were young or untrained men, the principes men in their full manhood, and the triarii veterans.