During the Crusades of the 11th Century, the Knights of St John received instruction in first-aid treatment from Arab and Greek doctors. The Knights of St John then acted as the first emergency workers, treating soldiers on both sides of the war of the battlefield and bringing in the wounded to nearby tents for further treatment. The concept of ambulance service started in Europe with the Knights of St John, at the same time it had also become common practice for small rewards to be paid to soldiers who carried the wounded bodies of other soldiers in for medical treatment.