Flank attack (Mil.), an attack upon the side of an army or body of troops, distinguished from one upon its front or rear. -- Flank company (Mil.), a certain number of troops drawn up on the right or left of a battalion; usually grenadiers, light infantry, or riflemen. -- Flank defense (Fort.), protection of a work against undue exposure to an enemy's direct fire, by means of the fire from other works, sweeping the ground in its front. -- Flank en potence (Mil.), any part of the right or left wing formed at a projecting angle with the line. -- Flank files, the first men on the right, and the last on the left, of a company, battalion, etc. -- Flank march, a march made parallel or obliquely to an enemy's position, in order to turn it or to attack him on the flank. -- Flank movement, a change of march by an army, or portion of one, in order to turn one or both wings of the enemy, or to take up a new position. -- Flanks of a frontier, salient points in a national boundary, strengthened to protect the frontier against hostile incursion. -- Flank patrol, detachments acting independently of the column of an army, but patrolling along its flanks, to secure it against surprise and to observe the movements of the enemy.