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.