Executive officer/Legends

In many militaries, an Executive officer (XO) was the second-in-command, reporting to the Commanding Officer (CO). The XO was typically responsible for the management of day-to-day activities, freeing the commander to concentrate on planning the unit's next move. The XO also took charge in the absence of the commander, and the position was frequently a stepping stone to a command position.

Some organizations use the term "Second-in-Command" or "First Officer" to describe an XO.