Triage

Triage is the sorting of casualties into order of treatment. The word comes from the French trier, to sort. It exists because in a mass-casualty event there are more patients than people and supplies to treat them all at once.

Most scholars credit Dominique-Jean Larrey, chief surgeon of Napoleon's Imperial Guard, with the first formal battlefield sorting system. In his memoir of the 1812 Russian campaign he wrote that the dangerously wounded should be treated first, "without regard to rank or distinction." Formal triage categories, colour-coded tags and protocols came much later. In between, sorting was improvised by whoever was in charge of the room.

At its simplest, triage asks three questions. Who will die without care now? Who can wait? Who will die whatever is done? The answers set the order of treatment and, when supplies run short, who receives them at all.

In Halifax in December 1917 there were no standard triage tags. At Camp Hill Hospital, Dr. George Cox walked the rows marking who needed surgery, then tied linen tags to patients recording their name, address, injury, treatment and what they would need next.

• Halifax, December 1917. Camp Hill Hospital, a 250-bed veterans' hospital, had more than 1,500 people lining its corridors. Cox's linen tags were an improvised record of sorting decisions.