In ancient times some of the great commanders were accompanied on their campaigns by their personal doctors. The Romans had at least one doctor for each cohort (about 500 to 600 men), and a legion, which consisted of ten cohorts, had a medicus legionis, probably a sort of chief medical officer. At the time of the Crusades, the Sultan Saladin gave an example of humanity by authorizing the doctors of the adverse party to care for the Christian prisoners and then to return through the lines. Arab doctors treated Saint Louis. But it was not until the sixteenth century that an organized medical service was started in European armies. It was still, however, sadly inadequate.