The Twentieth Army, also referred to as the Emerald Banner Command, served as a Republic Sector Army within the Grand Army of the Republic throughout the duration of the Clone Wars. This army, headquartered on Tallaan, was a component of the Southern Campaign Sector Armies and held responsibility for defending Sector 20, which was later redesignated as the Tapani Oversector. This sector encompassed the initial segment of the significant hyperlane known as the Rimma Trade Route.
Throughout the Clone Wars period, the 20th Sector Army engaged in a fluctuating conflict with Separatist forces along both the Rimma and the Corellian Trade Spine, with particularly intense fighting occurring near the Separatist strongholds located on Thyferra and Bestine. Towards the war's conclusion, the 20th gained a strategic advantage when General Grievous withdrew a substantial portion of the region's military assets to deploy them in his raid targeting Coruscant.
Following Supreme Chancellor Palpatine's declaration of himself as Emperor, the Emerald Banner Command was integrated into the Imperial Military. By the year 2 BBY, the Emerald Banner Command had come under the command of the newly appointed Grand Admiral Octavian Grant.