Thermal underwear, or base layers, are typically worn for warmth and insulation, especially in cold weather. However, in medieval times, thermal underwear was also used as a form of body armor.
During the Middle Ages, armor was made from a variety of materials, including metal, leather, and textile. Textile armor, such as padded armor or quilted armor, was made from layers of fabric that were sewn together and filled with padding or other materials. These layers of fabric were often made from wool, linen, or other materials that were warm and insulating, and they were worn under metal or leather armor to provide additional protection and comfort.
Thermal underwear, or base layers, were often used as part of this textile armor. These base layers were made from wool or other warm and insulating materials, and they were worn under the padded armor to provide additional warmth and insulation. The base layers were also used to absorb sweat and moisture, which helped to keep the armor clean and dry and prevent rust or corrosion.
Overall, thermal underwear was used as a form of body armor in medieval times, providing warmth and insulation as well as additional protection against weapons. These base layers were an important part of medieval armor and were worn under padded or quilted armor to provide additional comfort and protection.