Men who followed this path came to be known by a variety of names, including kenja , kenza , and shugenja . These mountain mystics came to be renowned for their magical abilities and occult knowledge, and were sought out as healers or mediums, known as miko .Most of these ascetics, in addition to their devotion to shugend , studied the teachings of the Tendai sect of Buddhism, or the Shingon sect, established by Kb Daishi in the 8th century. Shingon Buddhism was one of the primary sects of mikkyo () or Esoteric Buddhism, according to which enlightenment is found through isolation, and the study and contemplation of oneself, as well as nature, and esoteric images called mandala. Both the Shingon sect and the Tendai viewed mountains as the ideal place for this sort of isolation and contemplation of nature.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 shei , the yamabushi became warriors as well as monks.
It should not be surprising to find references to them fighting with bow and arrow, or with sword and dagger. However, like the shei and Ikk-ikki , the weapon of choice for the yamabushi was the naginata.
The mountain monks are known to have hired ninja to fight alongside them, and to aid them in various, more clandestine ways. And the ninja are known to have disguised themselves as monks or mountain ascetics, so as to pass unnoticed more easily in certain environments. Most likely, this is where the confusion can be said to have come from; it seems unlikely that any significant number of yamabushi would have been trained by the insular ninja clans in ninjutsu.
Source: Wikipedia > Yamabushi
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