Because of the prominence of the sect in Japan, people tend to think of Zen as being Japanese. It's actually a uniquely Chinese form of Buddhism (most scholars don't accept the view that Zen was ever brought from India) and it spread out from China to several other Asian countries, of which Japan was just one.

Japanese director Akira Kurosawa got a lot of mileage out of Shakespeare, transforming the Bard's plays into samurai epics. One of these is “Throne of Blood,” Kurosawa's samurai version of “MacBeth.”

The “Warring States” era in Japanese history was the time between the Onin War (which led to the collapse of central authority) and the eventual reunification of the country under Hideyoshi, Nobunaga and finally the Tokugawa shoguns. This “Warring States” period lasted for a century or so, depending on when you say it started and ended. The defining feature of the era was said to be “the low oppress the high,” meaning that many samurai disregarded the call of loyalty and overthrew their own masters to seize power for themselves. That makes it the perfect era for a retelling of MacBeth, with Toshiro Mifune as a samurai tempted to betray his lord and seize his province at the instigation of a creepy old ghost in the woods.

I've had several conversations with friends and family members who have expressed the opinion that militarism and authoritarianism are somehow “Western,” a product of “Western patriarchal thinking” or of Christianity. These same friends and family members tend to hold up Buddhism as an example of the “Eastern alternative” to our violent Western ways.

“Mushin” is a Zen-influenced concept in the Japanese martial arts, particularly the art of swordsmanship. The opponent moves to attack you and you suddenly perform a technically perfect counter that cuts him down with a single strike, yet you never consciously think about what strategy you're going to use. That's called “mushin” or “non-thought.”

“Ken zen ichi nyo” is a phrase often repeated in karate circles, where it is usually translated as “the body and the mind are one” or “the fist and Zen are one.” As “ken” means “a sword” in Japanese, it clearly doesn't mean either of these things. What it means is “the sword and Zen are one.”

This is essentially a cliché of Japanese swordsmanship, often repeated by people without any extensive experience of either Zen or swordsmanship. Historically, most Japanese swordsmen were not particularly familiar with Zen Buddhism, but would be expected to have some understanding of Mikkyo or “esoteric” Buddhism. Mikkyo contains a number of magic charms and spells to overcome fear or survive dangerous situations, so warriors were interested in using Mikkyo for what they believed to be practical purposes. Zen enlightenment was, to put it mildly, above their pay grade.