Kurosawa's last two samurai films are the tragedies, "Ran" and "Kagemusha". In terms of spectacle and scope, both are masterly, with each boasting set pieces to rival the rain-soaked battle that closes "Seven Samurai". Nevertheless, the spectacle here is only there to serve the story: a bleak, almost nihilistic vision that delivers a very different viewing experience from that of genre movies such as "Yojimbo". As the varying experiences of the reviewers here attests, "Kagemusha" is not a clear masterpiece, but there is a strong argument for counting it amongst Kurosawa's most substantial and impressive works.
In the hands of a Western director, the basic story (of a thief posing as a warlord's double) might well have been played purely for laughs. Indeed, within the sedate, solemn pacing of the film there is a lot of room for warmth and humour in the film's first half, but the later stages move strongly towards the desolation of "Ran", and the battle sequences offer no real release from the gloom. Indeed, the elaborately staged Battle of Nagashino (one of the most celebrated in Japanese history) exists within the film almost purely as a symbol of the clash between the Samurai period and the birth of a Modern, more ethically compromised, Japan. Those looking for suspense, action and swordplay will be disappointed.
I've seen this film several times over the years, and while there are several of Kurosawa's films that I enjoy more, I would place this right up there with his greatest. While some critics hold that Tatsuya Nakadai's performance is weaker than Toshiru Mifune might have given in the same role, this accusation strikes me as baseless; both here and in "Ran" Nakadai proves a genuinely masterly actor in his own right.
This will always be a film for a more patient and contemplative viewer, but I'd heartily recommend it.