Much of the film recounts actual historical events, including Shingen's death and the two-year secret, and the climactic Battle of Nagashino in 1575. Those scenes are also modeled closely on detailed accounts of the battle.
When Toho Studios couldn't fulfill the budget demands of the film, American film directors George Lucas and Francis Ford Coppola stepped in to help Akira Kurosawa. Kurosawa was visiting San Francisco in July 1978 and met Lucas and Coppola. The two convinced studio 20th Century-Fox, still riding high after the success of Lucas' Star Wars: Episode IV - A New Hope (1977), to advance-finance the film and fund the remaining portion of the budget. This was done in exchange for the film's world-wide distribution rights to the picture outside of Japan. This was the first time that distribution rights to a Japanese film had been pre-sold to a major Hollywood studio.
The battle scenes utilized hundreds of horses and thousands of extras. According to George Lucas, the picture had five thousand extras in the film's battle sequence finale which depicted the Battle of Nagashino of the year 1575.
Final feature film of actor Takashi Shimura. He was one of director Akira Kurosawa's favorite actors, and Kurosawa used him regularly. This movie was their final collaboration. Kurosawa wrote the part of Gyobu Taguchi in this film for him. The scene in which Shimura appears was cut from the international subtitled version of the film but has been put back in the modern subtitled DVD release. Shimura passed away in 1982.
This movie set in during the Sengoku Period of Japanese history. Also known as the Warring States Period, it went from around the mid-16th century (1500s) to the beginning of the 17th century (1600s). It was a period of constant political turmoil, social rebellion and military war. It eventually resulted in the creation of the Tokugawa Shogunate which unified regional politics and gave political stability to Japan.
Akira Kurosawa: [weather] There's a rainy scene just before the final battle of the film, not to mention the rainbow part which is one of the most memorable parts of the film.