The Fourth Outer Rim Army, also known as the 4th Sector Army, White Cuirass Command, and simply the Fourth Army, was a Republic and later Imperial Sector Army charged with the defense of Sector 4. Initially assigned to Sector 4 as part of the Reserve Sector Armies, the 4th Sector Army served as a reserve command for Republic campaigns in the Mid Rim and Outer Rim Territories during the Clone Wars. Late in the war, it became known as the Outer Rim Sector Army while serving alongside the 13th Sector Army in the Outer Rim Sieges. It contained Jedi General Ki-Adi-Mundi and clone marshal commander CC-1138's 21st Nova Corps. The 4th Sector Army eventually saw action within their own theater late into the Clone Wars, when it participated in the battle of Neimoidia.