A commanding officer — the senior officer who leads and gives orders to military units.
新しい司令官が任命され、部隊の士気が高まった。
A new commanding officer was appointed, and the unit's morale rose.
司令官は会議で作戦の変更を発表した。
The commanding officer announced a change of strategy at the meeting.
彼女は前線で司令官として多くの判断を迫られた。
She had to make many decisions as a commanding officer at the front.