The Eighteenth Army, also known as Night Hammer Command, was one of twenty sector armies that comprised the Grand Army of the Republic during the Clone Wars, the civil war between the Galactic Republic and the Confederacy of Independent Systems. In the late stages of the galaxy-wide conflict, the 18th Sector Army was placed under the command of Moff Wilhuff Tarkin, the Governor-General of Sector 18, and remained in military service after the Republic's transition into the first Galactic Empire.