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.