Samurai Dave – The Roving Ronin Report has an interesting article on the history behind Japanese horseback archery. What makes the text relevant to Kurosawa is the following paragraph, which discusses one of the two archery schools:
“The other archery school was begun earlier by Minamoto Yoshiari in the 9th century at the command of Emperor Uda. This school became known as the Takeda school of archery. The Takeda style has been featured in classic samurai films such as Akira Kurosawas Seven Samurai (1954) and Kagemusha (1980). The famed actor of many samurai films, Toshiro Mifune, was a noted student of the Takeda school.”
It would in fact be interesting to know to which extent Kurosawa actually researched matters like these.