
Originally Posted by
Stephen Turnbull, Samurai Warfare
It was the changes in warfare brought about by the experience of the Mongol invasions and the Nambokucho wars that broadened the base of samurai warfare. It became recognized that if the object of the excercise was to bring down a mounted samurai then the most efficient way of doing this was not to use another mounted archer, but to set against him half a dozen foot soldiers armed with naginata, kumade (rakes), or even bows.
How, then, was the samurai to defend himself? Hsi arrows would be at their least effective in such a situation, and his sword would have a very limited reach when dealing with foot soldiers, particularly if they lured him into the cover of trees and undergrowth, a form of terrain that characterized much of the fighting during the Nambokucho wars. The obvious answer was to provide the samurai with a polearm. The naginata, with its curved blade and short handle, was designed for slashing and so not very practical when wielded from the saddle. The obvious weapon was the straight spear. With a minimum length of about 3 metres, it could be used as a lance or as a slashing weapon when the occasion demanded.
As a result, by the 16th century, illustrations of mounted samurai depict almost exclusively the use of yari (spears) from horseback. There is the occasional naginata, and a few nodachi (extra long swords).
Samurai carrying bows are hardly ever illustrated or mentioned in the chronicles, and the fact that Shimazu Toyohisa carried one with him at the battle of Sekhigahara was considered sufficiently unusual for the chronicler to take particular note of it.