Combat engineers are one of the oldest branches in the U.S. Army, and the Military Academy at West Point was primarily intended to ensure that the Army had an adequate supply of engineer officers. Their main duties until the 20th century had to do with constructing coastal defense fortifications, bridging and ferrying operations, surveying, map making, and the planning of siege operations. In the 20th century, they branched out into mine warfare (on land and in coastal waters) and the operation of specialized combat engineering vehicles such as bulldozers, dump trucks and most recently, the M728 Combat Engineer Vehicle, the Armored Vehicle-Launched Bridge and the Armored Combat Earthmover.

While their main purpose is to do construction and demolition work (often under fire), combat engineers are trained and equipped to fight as infantry, although they have less in the way of support weapons (mortars, antiaircraft and antitank weapons) than regular infantry and therefore are usually committed to combat only when things have gone horribly wrong and someone, anyone, is needed to plug rapidly expanding holes in the line. Combat engineers may not be terribly book smart, but they are extremely good at working with their hands. During the Cold War, combat engineers had the MOS of 12B and 12C (bridging), but since then the field has absorbed various "civilian" construction MOS formerly in CMF 51, generator & power distribution specialists in CMF 52, heavy construction equipment operators formerly in CMF 62, and mapmakers in CMF 81.
