Dostoevsky was director Kurosawa Akira's favorite author. According to Kurosawa, nobody could depict humanity better. Therefore Hakuchi (The Idiot, 1951) was a passion project for Kurosawa, which he executed as a four-hour magnum opus. As you might guess, movie studios are rarely interested in these sorts of passion projects...
The Idiot was Kurosawa's first film for Shochiku after Scandal (1950). When he delivered his four-hour cut, the studio decided "nope", and edited a 100 minute (!) version out of it. Kurosawa was furious, and didn't make another film for the studio for 40 years. During the filming of Hachi-gatsu no rapusodi (Rhapsody in August, 1991), the director tried to locate a full cut from the studio archives, but the four-hour cut is apparently lost forever. Thankfully what remains for us later audiences, is not the 100 minute briefing by Shochiku, but an edit that lasts almost three hours. As always, it's difficult to say what an extra hour could have added to the narrative. But one thing is sure. At least you would not need to read intertitles in a sound film!
I recently read the Dostoevsky novel and watched a Soviet film adaptation by director Ivan Pyrev (1958). Perhaps Pyrev had witnessed Kurosawa's infamous 100 minute cut, and thereafter decided to not be an "idiot" himself, and to instead do the film in parts. Pyrev's adaptation only tells book one, and he never got to make a sequel for it. I thought his film was okay. As for the book, it wasn't among my favorite things by Dostoevsky, whom I usually adore. I would recommend Kurosawa's film for anyone who happened to like the novel. If you haven't read it, you are going to be a little confused. Imagine how confused the Japanese audiences must have been upon witnessing the 100 minute cut...
Kurosawa's film is interesting, because it differs from anything else that he directed. Partly this comes in the form of negative things. Both the source material and the editing-history make this an unusually unsure film for Kurosawa. The novel doesn't have much actually happening, which is very unlike your typical Kurosawa narratives, that are straight-forward.
Yet the best things in this adaptation are really great. Kurosawa's black and white depiction of winter in Sapporo is stunningly beautiful and helps to capture the emotional coldness of the narrative. The casting is also mostly excellent, once you get used to the fact that General Epanchin's wife is now the grandmother from Tokyo Story (1953). Hara Setsuko has been cast against type as the femme fatale, and this insane contrast serves to keep the film constantly interesting when she is onscreen. Hara is a movie star on the same level with Greta Garbo, and offers magnificent close-ups throughout the film. Mifune's rough temper is also perfect for the role of Rogozhin, and he does great job. Kuga Yoshiko also gives a good performance.
The only one, about whom I have reservations, is Mori Masayuki as the lead character, Prince Myshkin in the novel. In all his versatility, Mori is one of my favorite actors from Japan, but in this version the lead character has been written to be too undetermined. Myshkin as a character is kind, but also verbally talented, and therefore the way Kurosawa has directed Mori to look at everything like a confused puppy didn't really work for me.
Because I am not a great fan of the novel, it is difficult for me to say, what should have been added to make this a better film. It is clear that the first meeting of Mifune and Mori in the beginning has been drastically edited, and other introductions, too, seem to have been cut, making the film more confusing. It is interesting to wonder, if Shochiku had allowed Kurosawa to release the four-hour cut, had he done the film AFTER Shichinin no samurai (Seven Samurai, 1954)...
