Originally, Akira Kurosawa was planning on building merely a facade castle for the film, but this proved to be an impractical step, prompting the building of full castle sections to use in shooting. These were built with the help of United States Marines who were based in the area.
Takeshi Katô (Guard killed by Washizu) was worried about the thrust of Toshirô Mifune's sword, so he placed a block of wood in his arm pit. Unfortunately Mifune's thrust split the block and wounded Katô. He bore the scar until his death in 2015.
The story is based on William Shakespeare's early-17th-century play Macbeth, which was, in turn, based on a medieval Scottish legend.
In Japan, the title of "Throne of Blood" is "Kumonosu-jou" which translates into "Castle of the Spider's Web."
Akira Kurosawa believed that Scotland and Japan in the Middle Ages shared social problems, and that these had lessons for the present day. Moreover, Macbeth could serve as a cautionary tale, complementing To Live (1952).
Akira Kurosawa: [weather] Like in most of Kurosawa's films, rain plays a part in scenography, particularly during the misty forest sequences.