The United States Army Corps of Engineers (USACE) is an engineer formation of the United States Army that has three primary mission areas: , military construction, and civil works. The day-to-day activities of the three mission areas are administered by a lieutenant general known as the commanding general/chief of engineers. The chief of engineers commands the Engineer Regiment, comprising combat engineer, rescue, construction, dive, and other specialty units, and answers directly to the Chief of Staff of the Army. Combat engineers, sometimes called sappers, form an integral part of the Army's combined arms team and are found in all Army service components: Regular Army, National Guard, and Army Reserve. Their duties are to breach obstacles; construct fighting positions, fixed/floating bri