Executive officer
An executive officer is a person who is principally responsible for leading all or part of an organization, although the exact nature of the role varies depending on the organization. In many militaries and police forces, an executive officer, or "XO", is the second-in-command, reporting to the commanding officer. The XO is typically responsible for the management of day-to-day activities, freeing the commander to concentrate on strategy and planning the unit's next move.