At the very least, Akira Kurosawa's new martial epic, "Kagemusha," opening today at the Avalon 1, is the year's most impressive pictorial spectacle.

Only a director of exceptional vision and resourcefulness could manipulate a few hundred well-drilled and magnificently costumed extras with the dynamic grandeur sustained in image after image by Kurosawa, now 70. The director of "Rashomon" and "Seven Samuri" has created the transporting illusion that legions of cavalrymen, lancers and fusiliers, representing three different armies, are contending for supermacy in feudal Japan of the 1570s.

The Japanese title is rendered as "The Shadow Warrior" in English. Nobly conceived, splendidly visualized and often brilliantly acted -- especially by Tatsuya Nakadai in the demanding dual role of a feared warlord and his fearful peasant double -- "Kagemusha" is such a gratifying come-back picture for a justifiably revered filmmaker that one feels churlish harboring certain reservations.

"Kagemusha" is Kurosawa's interpretation of the moral and military decline of the Takeda clan, decimated on May 21, 1575 at the Battle of Nagashino. This historic slaughter is depicted in the climatic sequence in a boldly impressionistic yet anticlimatic style that may prove the most controversial device in the film -- impressing some viewers as an abstract distillation of battlefield horror and others as lofty miscalculation. The once-invincible Takeda calvalry is wiped out by the sustained riflepower of the allied Tokugawa and Oda clans, applying weaponry and tactics recently acquired from trade agreements with the Portuguese.

Three years earlier, a sniper's bullet foreshadows the rout at Nagashino. Wounded while paying a visit to his troops, clan tyrant Shingen Takeda fails to recover. He leaves instructions with his generals to conceal his death for three years, lest the rival clans be tempted to attack and the Takeda be demoralized.

Nobukado, Shingen's younger brother, has impersonated the warlord on many occasions. But he fears he could never sustain an impersonation within the royal household or ranks of the army. Fortunately, it would appear, Shingen and Nobukado have taken the precaution of securing another double: a condemmed thief spared from crucifixion because of his remarkable facial resemblance to the warlord. When Shingen dies, this low-born lookalike is compelled to assume his identity.

The impostor is our surrogate within this remote, militaristic society: a humble, ignorant, scared outcast, redeemed by his compassion and eventual self-sacrifice. Although a pawn in the historical scheme of things, he looms as a larger-souled human being than the great warrior he impersonated.

Rumors persist that Shingen has died; but the impostor plays his role with remarkable success, using a saving native wit to rescue himself from situations that can't be finessed by appearances.After a narrow escape, one of the Takeda generals remarks, "Sometimes a witty man depends too much on his wits. tHe must stay within the limits of his role."

A foolish act of pride ultimately exposes the impostor, returning him to the society of menials and vagabonds. The major hitch in Kurosawa's dramatization is a failure to link the impostor's deepening emotional commitment to the deception with the doomed fortunes of the clan. That downfall seems predetermined by the very decadence of Shingen's rule -- which substitutes his ongoing myth for fresh leadership -- and by an advanced battlefield technology.

When the impostor is banished and disgraced, it requires some awkward manipulation to get him on the battlefield to share in the climatic defeat. In addition, Kurosawa has diffused the emotional impact of his most decisive dramatic sequence: a night battle in which the impostor realizes the enormity of the role he's assumed. Watching from his seat of honor, the false Shingen is mightily tempted to bolt at the sounds and activities flashing around him in the dark. He is calmed by loyal retainers, who also close around him and take casualties when a raiding party draws dangerously close. Their sacrifice is meant to make an indelible impression on both protagonist and audience.

Given this grave moment of truth, it seems rather counterproductive to have the impostor lose his status in an almost offhand fashion and then play catch-up as a camp follower down the stretch.

Despite lapses in the plot, the heroic scale of the conception and Nakadai's marvelous performance may overwhelm any objections. The final image carries a summarizing symbolic wallop that seems to imply in a grandiose way. Nakadai is a riveting, unexpectedly funny presence, with flashing dark eyes as wickedly expressive as Zero Mostel's. He maintains humane contact even when the director's formality threatens to become suffocating.

For example, Nakadai's angry outburst at the close of the prologue, shot in one long static take with three figures seated at the edges and midpoint of the frame, breaks up a deliberately formal arrangement with explosive theatrical effectiveness. It also provides a vivid contrast with Nakadai's own elegant embodiment of Shingen, the figure in the center, whose movements are beautifully coordinated with those of Tsutomu Yamazaki as his devoted brother.

Kurosawa has come a long way back from the mawkish doldrums of "Dodes Ka-Den" and the serene platitudes of "Dersu Uzala," his only other completed projects over the past decade. If "Kagemusha" falls short dramatically, and many admirers may not share that impression, the sag occurs at an awesome level of filmmaking prowess. Ironically, this tale of a shadow warrior is diminished only by the length and intensity of the artistic shadow thrown by Kurosawa in his prime.