This is an extraordinary film combining great scenario and incredible visual effects, made by THE great master of Japanese cinema Akira Kurosawa. Below, more of my impressions, with some SPOILERS.
"Kagemusha" is the story of just three years of the incredible and extremely intense saga of Takeda clan. The period of great importance of Takeda was in years 1536-1582, but this film tells just the story of the dramatic years 1573 to 1575, from the siege of Noda castle to the battle of Nagashino. In order to better understand the events described in "Kagemusha" it is helpful to know the main events of the history of the Takeda clan in the previous years, as they are ocassionally referred to, but not fully explained.
In 1536 Takeda Nobutora, the head of Takeda clan, was the daimyo of impoverished mountainous province of Kai. Not only was this province a dirt poor backwater, but the Takeda didn't even really control all of it, as some of their nominal retainers, like the Hirada family, were in fact completely independent. Therefore the Takeda were really just a little, not very wealthy provincial samurai clan, without much importance. In 1536 Takeda Nobutora lost an important battle against the Hirada family, but soon after Takeda Harunobu, his then barely 15-years old son, avenged the defeat and destroyed completely the Hirada, greatly strengthening the position of his clan.
That great achievement notwithstanding, there was not much love between father and son and Harunobu, although being the oldest son, was not designed as heir - that position went to his younger brother Nobushige instead. Refusing this, Takeda Harunobu in 1541 seized the power and banished his father. Both his younger brothers decided to stay in Kai and remained loyal to Harunobu - when "Kagemusha" begins, Nobushige was already dead (see below) but second brother, Nobukado, is one of the main characters in the film. Takeda Nobuzane, his half-brother, who was still a child at that moment, also was going to serve him loyally once fully grown up.
The new leader was very ambitious and even if he had now all the Kai under his control he immediately attacked other daimyos from the neighboring province of Shinano, destroying first the Murakami clan. His next target was the Suwa clan, comprehensively defeated in 1542 - their leader, Suwa Yorishige, was taken prisoner and later murdered. Of all the Suwa clan only the daughter of Suwa Yorishige survived (we don't know her name - she is known only as Lady Suwa). Impressed by her beauty Takeda Harunobu took her as a concubine and she gave him his favorite son, Takeda Katsuyori, who is another important character in the film.
Having completed the conquest of Shinano province and having signed the alliance with the powerful daimyo Imagawa of Suruga, young Harunobu beacame a very famous and powerful warlord - from that moment he was called "The Tiger of Kai". It was at that time that encouraged by his main strategist, Yamamoto Kansuke, he had made a new war banner, under which the Takeda clan would fight from now on - and which would become a legend in its own. This banner was called "Furin Kazan", from characters signifying "Wind, Forest, Fire, Mountain" and the flag itself carried the inscription taken from Sun Tzu's writings, precising the characteristics necessary for a great general: "Fast as the wind, silent as the forest, ardent as the fire, calm as the mountain".
His next target was the province of Echigo and its young lord Nagao Kagetora, who had the particularity of being not only an exceptionnal warrior but also a buddhist monk, better known under his religious name Uesugi Kenshin and also called "The Dragon of Echigo". The long confrontation between the "Tiger of Kai" and "Dragon of Echigo" lasted 14 years, roughly from 1550 to 1564. During this time they fought no less than five battles at the Kawanakajima plain!
In 1559 Takeda Harunobu decided to become himself a novice Buddhist monk and took a new name - from that moment on he was known as Takeda Shingen.
The culmination of the confrontation between the Takeda and Uesugi armies was the fourth battle of Kawanakajima, in 1561, in which at one moment Takeda Shingen and Uesugi Kenshin fought one against other, swords in hand! Takeda Shingen was wounded during this fight - and as you will see, the scar from this wound plays an important role in "Kagemusha" plot. The battle itself however was a draw - Uesugi Kenshin lost more soldiers (4000 against 3000 for the Takeda clan) but he could withdraw without being bothered by exhausted enemies. The Takeda clan lost also two precious generals - the famous strategist Yamamoto Kansuke and Shingen's loyal younger brother, Takeda Nobushige.
Realizing that his fight against Uesugi Kenshin is a dead end, Takeda Shingen made peace with his old nemesis in 1564. Uesugi Kenshin appears briefly in "Kagemusha" without being openly named - you will recognize him by his impressive monastic clothes and the buddhist rosary he always held in hands. Both warlords needed peace because a new power was rising in Japan: Oda Nobunaga, the terrifying and somehow extravagant daimyo of Owari, who apears a lot in "Kagemusha" (including a greatly hilarious scene in which he and his guest taste some Portuguese wine or like they call it "barbarian sake"...).
In 1560 Oda Nobunaga greatly weakened the powerful Imagawa clan from Suruga by winning the battle of Okehazama. Seeing that Suruga province was now ripe for picking, Takeda Shingen betrayed his Imagawa allies and finally seized this precious land in 1569. The Takeda clan was now a major power and one of two top pretenders to the control over all Japan. The only rival of the Takeda was the alliance between Oda Nobunaga and a young daimyo from Mikawa, a certain Matsudaira Takechiyo, who in 1567 changed his name and became Tokugawa Ieyasu - this latter famous character also appears in "Kagemusha"...
In 1567 Takeda Yoshinobu, Shingen's oldest son by his wife, Lady Sanjo, rebelled against his father resenting his favouritism towards Katsuyori. Easily defeated, Yoshinobu was forced by his father to commit seppuku.
After defeating Oda Nobunaga and Tokugawa Ieyasu in some minor engagements and in the major battle at Mikatagahara on 25 January 1573, Takeda Shingen besieged, at the end of January 1573, the castle of Noda defended by 500 men loyal to Tokugawa Ieyasu. This is AT THAT MOMENT THAT "Kagemusha" BEGINS - and I will not say much more about the action of the film.
"Kagemusha" means "the shadow warrior" and in feudal Japan was the word designing the decoys used by some warlords to impersonate them in various occasions, to avoid risks of assasination or to let them recover in peace from sickness or simply to allow them to catch a moment of rest during the campaign... The use of "kagemushas" was a common practice and it gave of course occasion to some wild rumors - according to some of them, Tokugawa Ieyasu himself was supposedly killed at the second siege of Osaka in 1615 and during the following 12 months was replaced by a decoy, the time that his power is safely transmitted to his son (that story is almost certainly NOT true). In our times the decoys are also used - the most famous was certainly Clifton James, a simple soldier who for a time impersonated Montgomery, in order to deceive Axis intelligence services...
This film tells the story of a fictitious "kagemusha", as Takeda Shingen was not known for using one. Both Shingen and his double are played by the great Japanese actor Tatsuya Nakadai - and as always, he does a great job. Other important characters are Takeda Nobukado (Shingen's younger brother), Takeda Katsuyori (Shingen's favourite son) and Takemaru (real name Takeda Nobukatsu), Shingen's grandson, aged 5 at the beginning of the film.
Takeda Shingen was famous for gathering around him 24 excellent commanders, known as Twenty Four Generals of the Takeda. In 1573, when the film begins, many were already dead, so in this film we see only seven of them, including Takeda Nobukado. The most important character amongst them is Yamagata Masakage, the old man with red face. Two other real generals I managed to identify were Hara Masatane and Naito Masatoyo. Those are the three generals who at one moment cross their lances together, in an extremely powerful scene towards the end of the film.
Other than the scenario, which is excellent, as always in Kurosawa films, the great treasure of this film are the images. Samurai armies are impressive, battles are even better and the sequences of the dreams (or rather nightmares) are very powerful.
The final scenes of the great battle of Nagashino are of course a very beautiful thing from the artistic point of view, but the REAL battle was absolutely NOT such an one sided affair as it is pictured. Kurosawa needed to adapt this battle to obtain a Wagnerian finale and also there is no question that this battle ended with a great disaster for one of the sides - but still, in real history, things went VERY differently from what we see in "Kagemusha".
On another hand, the character of Oda Nobunaga is IMPRESSIVELY good! In this film he appears really as a warlord for whom thousands would be ready to rise, fight - and die.
The film doesn't say (sorry SPOILER coming) what would happen later to three of the most important characters, Takeda Nobukado, Takeda Katsuyori and little Takemaru (yes, here is the SPOILER - they survive to the final credits). And honestly I would advise you to NOT research this question before watching "Kagemusha". Do it after. Believe me, it is a good advice.
CONCLUSION: this film is a masterpiece; it lasts 3 hours but at the end you will only feel sorry that there is no more; a film to buy, watch, keep and re-watch. Enjoy!