Barbette

A barbette is a protective circular armour feature around a cannon or heavy artillery gun. The name comes from the French phrase en barbette referring to the practice of firing a field gun over a parapet (defensive wall) rather than through an opening (embrasure). The former gives better angles of fire but less protection. For example, the Confederate defenders at the Second Battle of Fort McAllister were unable to operate their cannons because the en barbette gun emplacements provided poor protection from Union riflemen outside the fort.