The technology that led to the development of the Japanese sword originated in China and was brought to Japan by way of Korea. The oldest steel swords found in Japan date to the fourth or fifth century A.D. Although appearing to be ceremonial in nature, samples of these straight blades preserved in the Shōsōin were hand-forged with hardened cutting edges. By the time of the Heian period (794—1185 AD) the Japanese sword took on its distinctive curved shape as a mounted horseman would have more use for a slashing type of blade as opposed to a thrusting type. These swords were known as "tachi".