to stop external arterial bleeding and airways are adjusted to ensure un-obstruction as they are carefully moved to a medical staging area, usually with the aid of those marked green or unable to provide medical assistance. : Individuals listed as black have died. The person's pulse and breathing is checked to confirm no vitals present. In low-scale disaster with few victims involved, immediate CPR is started in attempt to revive the vital signs. In larger events with more victims, the head is positioned to open the airway, the body is rolled onto its side and the responder will move on to the next victim. The positioning is done so if the body's vitals return, vomiting will not be as likely to choke the victim. The bodies will not be collected until all surviving individuals have been removed from the immediate disaster area. There will be a body collection staging area set up away from any medical staging areas. Usually this will begin the recovery phase. United States military A battlefield situation, however, requires medics and corpsmen to rank casualties for precedence in MEDEVAC or CASEVAC. The casualties are then transported to a higher level of care, either a Forward Surgical Team or Combat Support Hospital and re-triaged by a nurse or doctor. In a combat situation, the triage system is based solely on resources and ability to save the maximum number of lives within the means of the hospital supplies and personnel. The triage categories (with corresponding color codes), in precedence, are: : The casualty requires immediate medical attention and will not survive if not treated soon. Any compromise to the casualty's respiration, hemorrhage control, or shock control could be fatal. : The casualty requires medical attention within 6 hours. Injuries are potentially life-threatening, but can wait until the Immediate casualties are stabilized and evacuated. : "Walking wounded," the casualty requires medical attention when all higher priority patients have been evacuated, and may not require stabilization or monitoring. : The casualty is expected not to reach higher medical support alive without compromising the treatment of higher priority patients. Care should not be abandoned, spare any remaining time and resources after Immediate and Delayed patients have been treated. Afterwards, casualties are given an evacuation priority based on need: Urgent: evacuation is required within two hours to save life or limb. Priority: evacuation is necessary within four hours or the casualty will