During the Napoleonic Wars (1803–1815), the French established a tiered system of medical support services. Basic aid stations operated by one field medic were established as close to front lines as possible, sometimes within a few hundred meters to allow for the treatment of wounded troops as soon as possible. The more seriously injured were transported further back behind front lines to field hospitals in churches or nearby chateaus. Those who required more extensive treatment were transported again to much larger permanent "receiving" military hospitals in France.