Takeda Nobukado (武田信廉)(d. 1575) was a brother of Takeda Shingen, and one of his 'Twenty-Four Generals'. Nobukado commanded the Takeda central comapny in the Battle of Nagashino, and was killed in that battle. Events February 13 - Henry III of France is crowned at Reims February 14 - Henry III of France marries Louise de Lorraine-Vaudémont August 5 - Henry Sidney is appointed Lord Lieutenant of Ireland. ... Takeda Shingen (武田 信玄 Takeda Shingen) (December 1, 1521 – May 13, 1573) of Shinano and Kai Provinces, was a preeminent daimyo who fought for control of Japan during that countrys Sengoku or warring states period. ... The Battle of Nagashino in 1575 took place in Nagashino in Mikawa of Japan. ...
Reference
Turnbull, Stephen (1998). 'The Samurai Sourcebook'. London: Cassell & Co.
The shadowed warlord of the story is based on Daimyo Takeda Shingen and the climactic fight on the Battle of Nagashino which took place in 1573 (source: [1]).
The film was released in 1980 and is generally considered a great costume reincarnation of feudal Japan with its endless warlordism as well as the story of a man with a divided personality, or more generally that of an actor who falls too deep into his role.
Nobukado presents the thief to the generals and contrives a plan to have the kagemusha impersonate Shingen full-time.