The UNSC Corps of Engineers (ENGCORP) is a cross-service formation of the United Nations Space Command Defence Force comprising of the engineering and maintenence battalions of the UNSC Army and Marines, the Engineering Officers of the Air Force, and the Construction Battalions (Seabees) of the Navy. Commonly known as the Sappers, it provides military engineering and other technical support to the UNSCDF, and is also responsible for surveying viable planets for colonisation or terraforming.