Imperial Army:
The Imperial ground forces, sometimes incorrectly refered to as the Imperial Army, was a branch of the Imperial Military that had the primary responsibility of prosecution of ground-side military operations, under the oversight of Army Command. It was formed by re-organizing the Grand Army of the Republic and kept its previous command structure. During the Imperial era, one of the Army's most common duties was the maintenance of planetary garrisons throughout the galaxy, as well as waging war on the Alliance to Restore the Republic.
The Army utilized a wide range of equipment and vehicles in support of its infantry. Army units were often reinforced by stormtroopers, although the command structure for the two organizations remained separate. On garrisoned worlds, the Army operated in conjunction with Imperial Starfleet, stormtroopers, and the local constabulary to maintain order and security. -Wookieepedia
