In their mountain retreats, these monks studied not only nature and religious/spiritual texts and images, but also a variety of martial arts. Whether they felt they had to defend themselves from bandits, other monks, or samurai armies is questionable, but the idea of studying martial arts as a means to improve oneself mentally and spiritually, not just physically, has always been central to Japanese culture, beyond the specific tenets of one religious sect or another. Thus, like the sōhei, the yamabushi became warriors as well as monks.