1. Stretcher bearers - 4 per stretcher usually, 16 per battalion of 1,000 men, did first aid
2. Regimental Aid Post - in a dugout, 1 medical officer, gave immediate first aid
3. Dressing stations - in abandoned buildings or tents, 10 medical officers, could look after a person for up to a week
4. Casualty Clearing Station - triage, mini hospitals with x-ray machines, capable of performing operations
5. Base Hospitals - near the coast, for experimental medicine and long-term care
6. Underground hospital at Arras - space for 700 patients, operating theatres, railway, electricity and water