During Medieval times military trained surgeons saved as many lives as they could on the battlefield. Ideas from the East (learned from Muslims during the Crusades) such as using wine and a cauterising iron to seal up wounds and stop bleeding. The use of wine for cleaning a wound (antiseptic) was discovered by Hugh and Theodoric of Lucca.
Surgery continued to be simple and on the external parts of the body, as it had been in Ancient times.
Most surgery was performed by barber-surgeons who not trained doctors. In this period there was a lot of opposition to surgery.
In the Islamic world in the Medieval period Greek books were translated into Arabic, and many medical books were written by surgeons. Operations were more common, even the removal of bladder stones! Any improvements in surgery were few and slight due to the ban on dissection in the East and the West.