A tachi is a long Japanese sword with greater curve and more taper from the hilt. The weapon was about 70-80 cm long and was lighter in weight then the later katana. Tachi are sometimes thought to have been used as cavalry weapons, with the long curved blade being ideal from cutting down foot soldiers from horseback. Tachi were generally used prior to the adoption of the katana as the standard samurai swords, seeing use in the Genpei War, with marked the end of Heian period (794-1185) and beginning of the Kamakura period (1185-1333), as well as during the failed Mongol invasions of Japan in 1274 and 1281.