The incident commander is the person responsible for all aspects of an emergency response; including quickly developing incident objectives, managing all incident operations, application of resources as well as responsibility for all persons involved. The incident commander sets priorities and defines the organization of theincident response teams and the overall incident action plan. The role of incident commander may be assumed by senior or higher qualified officers upon their arrival or as the situation dictates. Even if subordinate positions are not assigned, the incident commander position will always be designated or assumed. The incident commander may, at their own discretion, assign individuals, who may be from the same agency or from assisting agencies, to subordinate or specific positions for the duration of the emergency. In the United States, most agencies use an Incident Commander for the roles and responsibilities as defined under the National Incident Management System as a part of the Incident Command System