The Tachi is a traditional Japanese sword that originated in the Heian period (794-1185 AD). It is characterized by its long, slightly curved blade and its handle, which is longer than that of a katana. The Tachi was designed to be used by samurai warriors on horseback, and its length and shape made it efficient for use in slashing attacks from horseback.

The Tachi was also often used as a symbol of social status and power, and was worn by high-ranking samurai during ceremonies and important events. It was often decorated with intricate designs and motifs, and some Tachi even had jewels embedded in their hilts.

In the late 12th century, the Tachi was gradually replaced by the katana as the primary weapon of choice for samurai warriors. However, the Tachi remained a popular status symbol and ceremonial weapon for many centuries.

Today, Tachi swords are highly sought after by collectors and enthusiasts, due to their historical significance and exquisite craftsmanship. Some of the most famous examples of the Tachi include the "Sanjo Munechika," the "Heshikiri Hasebe," and the "Fudo Masamune."