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.
Samurai women often received martial training of their own, and were expected to cultivate the same kind of warrior mentality as the men. However, they were given no political authority at all. That's the perfect recipe for creating a samurai equivalent of Lady MacBeth- ruthless, unscrupulous, manipulative and determined to exercise power from behind the scenes.
All the ingredients were in place, and all Kurosawa had to do was to get a good script together, use some great actors, and apply his own directorial genius. The result is “Throne of Blood,” my personal favorite version of the story of MacBeth.