The seax was originally a belt/utility knife. Swords were extremely rare and expensive in the 5th-11th century because of a lack of quality ores and lack of skilled weaponsmiths. The seax was often pressed into service as a backup weapon because swords of the day were often brittle and the edges wore down quickly in combat. As viking raids became more prevalent, the seax grew into a singled-edged short sword and was pressed into service with a spear and shield. The seax's singled-edged design allowed for a thicker spine and a more durable weapon.