It may seem a misnomer to describe a warrior as being 'Zen.
' The fact is though is that the Eastern martial arts as we know them today were developed as a means of self-defense first by Buddhist monks in China who were being attacked by mountain bandits along country roads.
Later, the practices spread and became more secularized.
By the time the samurai were being trained in 'bushido,' which is straight from Zen, monks were no longer fending off mountain bandits.
On the outside they were pacifists.
But politics, being what they are, eventually procured monks as trainers of warriors, known to us as Samurai and Ninja.
Like all warriors, the samurai had two facets to the discipline: fighting technique and a code of honor.
In war, obviously, it is preferable to come out the winner in a battle and so deadly fighting techniques were practiced by the Samurai day and night.
Like all martial arts, 'bushido' consists mainly of close range fighting, with the addition of weapons instead of just hands.
Ninja had to be exceptional people from the very start, and only the very best of the Samurai recruits were destined to become Ninja.
The stealth and invisibility of a Ninja were likewise the result of rigorous training established by Zen.
The code of honor that Samurai lived by had much more to do with the secular world and Confucian values than anything with Zen or Buddhism.
This code was a refinement of already extant societal values and elaborated to conform the military ethics of engagement.
Zen had a profound effect on Japanese culture in all aspects, including civil war.
It is not so much that Buddhism had become aggressive during this time as that as a very large institution affecting the whole populace it was subject to many pressures from without, one of these being the training of warriors.