By the end of a battle, both captives and captors were likely to be wounded. Those who had taken prisoners could not benefit from their acquisitions unless both parties survived, which was more likely if they received some medical care. Basic knowledge of practical wound treatment was widespread among medieval soldiers and indeed among aristocratic women. Arrows and javelins that had not gone in too deep were usually pulled out (or pushed through) as quickly as possible, often by the injured person. Wounds were washed with vinegar or wine—effective antiseptics—to remove any possible source of infection (dirt, cloth, etc.), then covered with moistened lint, plasters, egg, or lard-based ointments, then bandaged, often with strips cut from a shirt. Sometimes herbal poultices would also be used. Later, the wounds would be washed and re-bandaged frequently, with any corrupted flesh being cut away. This was quite effective; in one sample of over 300 skulls dating from the sixth through the eighth centuries, only twelve percent of the wounds showed any evidence of infection.
Armies in the field were usually accompanied by physicians, surgeons, and barbers (who provided basic medical care). Great lords typically brought such men as part of their retinues, and infantry contingents often did the same. Medical personnel doubtless gave first priority to their own employers, but it was normally expected that wounded soldiers would eventually be tended by a physician if necessary: to say someone had been struck with such force that he would have no need of a doctor was to say that he had been killed outright. Despite the common belief to the contrary, western European surgeons of the Middle Ages seem to have been roughly on a par with their Islamic, Byzantine, and Jewish contemporaries. They could stop the bleeding of a cut artery with pressure and cauterization; they were skilled at treating broken skulls using trepanning; they could draw out barbed arrows using metal tubes or goose quills to cover the barbs; they knew how to splint smashed arms or legs. They could even suture intestines or severed jugular veins. They had analgesics and anesthetics made with opium, cannabis, and other less powerful substances….
— Clifford J. Rogers, Soldiers’ Lives Through History, pp. 224-25