Japanese Yari (Spear) Tactical System

Timeline

1. c. 1300–1390Various parts of Japan · JapanFrom the late Kamakura period through the Nanboku-chō period, straight-bladed yari began appearing on Japanese battlefields as infantry weapons. Initially, mounted warrior tactics centered on the naginata were gradually supplemented by long spears, used mainly as thrusting weapons against armored warriors.
2. 1467–1477Kyoto · Kansai regionDuring the Ōnin War (1467–1477), hiring ashigaru (foot infantry) as the main force became common. Dense formations of ashigaru wielding yari first appeared in street fighting and positional warfare inside and outside Kyoto, laying the groundwork for the infantry spear tactics of the Warring States period.
3. 1511–1520Daimyō domains across Japan · JapanBetween 1511 and 1520, Warring States daimyō such as the Hōjō, Imagawa, Takeda, and Ōuchi had standardized ashigaru spear formations. Yari lengths increased to 3–5 meters or more (ōbi-yari), advancing in ranks side by side to counter cavalry charges and enemy spear formations. Combat shifted from individual warrior duels to massed infantry engagements, with the spear becoming the decisive weapon, and organizational discipline and formation training were institutionalized accordingly.
4. 1575–1615Nagashino (Mikawa Province) · Mikawa ProvinceIn the 1575 Battle of Nagashino, Oda Nobunaga used three-rank volley fire from firearms combined with defensive spear formations to rout the Takeda cavalry, bringing ashigaru spear tactics to their tactical peak. Thereafter, the coordination of firearms and spears became the standard of early-modern Japanese tactics, until the Edo shogunate ended large-scale warfare and the spear's function became ceremonial.