AGMEN, in Antiquity, properly denotes a Roman army in march; in which sense it stands contradistinguished from acies, which denoted the army in battle array; though, on some occasions, we find the two words used indifferently for each other. The Roman armies in their marches were divided into primum agmen, answering to our vanguard; medium agmen, our mainguard; and postremum agmen, the rearguard.