"Action stations" describes a state of readiness in which the ship is prepared to go into battle. When the captain calls for action stations, the sound of marine drums and the bosun's call for "action stations" will be heard throughout the ship. When the sound is heard, all officers and crew must proceed immediately to their assigned action stations. For officers, these action stations are assigned based on their rank aboard ship or, in cases in which two officers have the same rank or in which an officer is missing or incapacitated, seniority.