As 2nd in command and Chief of Staff (CofS), the Executive Officer (XO) is prepared to assume the duties of the commander when the need arises. He is the commander’s principal assistant for directing, coordinating, supervising, and training the staff, except in areas the commander reserves. The XO frees the commander from routine details and passes pertinent data, information, and insight from the staff to the commander and from the commander to the staff.
(FM 3-09.21, 1-10; FM 100-5, 4-2)