More than once in Sergei Eisenstein’s “Alexander Nevsky,” the titular 13th-century hero appears to stare down right into the audience as he delivers his solemn exhortations to the people. That’s no accident, because the audience, of course, was “the people” — namely Soviets in 1938 facing a rising Nazi regime. Eisenstein’s film was a functionally and folksily rousing piece of socialist realism, in line with the imperatives of the country’s most executive of producers: Stalin.

It was also, for Eisenstein, an attempt to right his reputation after years of filmmaking misfortunes, such as the previously halted production of “Bezhin Meadow.” That vulnerability, plus the topical propagandist impulse, make “Alexander Nevsky,” which opens for a weeklong engagement Friday at Film Forum, one of the foundational director’s most straightforward works — neither as dazzling as the pioneering “Battleship Potemkin” (1925) nor as mystically fervid as his subsequent historical epic, “Ivan the Terrible” (1944).

But his overtly patriotic film is still a work of concerted artistry, and one that only reaches its full potential on the big screen. In Nevsky’s practically rectangular frame, which is populated by waves of villagers and battle lines drawn on a frozen lake, the visuals of the medieval Russians’ resistance against Teutonic invaders command the screen like a series of billboard-size storyboards. Further, for his first complete sound film, Eisenstein unified his vision with a celebrated score by Sergei Prokofiev.

The movie’s prologue sets the theme of indomitable land-loving patriotism: Nevsky, so named for vanquishing the Swedes at Neva but now living in a fishing village, rebuffs a silver-tongued Mongol leader. When the menacing Teutonic knights invade Pskov near Novgorod, pillaging and tossing babies onto bonfires, Nevsky is brought on as leader after a didactic town-square debate. The walking icon (played by the popular comedian Nikolai Cherkasov) explains to the people that they don’t have to love him; he’s there to lead them into battle. At the time, they were prophetic words both inside and outside the movie, considering where the Soviet Union was headed in the years following 1938.

The first 30 minutes of “Alexander Nevsky” roll out a few hearty salt-of-the-earth types — two galoots vying for a pigtailed girl, and a rascally oldster quoting proverbs — for relatable purposes that the story revisits later, but it’s all really a ramp-up to the movie’s centerpiece: its iconic battle on ice, which became an instant folk legend. Eisenstein staged the scene both from a distance and from within the fray. First, the far-off Teutonic line advances like a fattening horizon line as Russian soldiers wait and sway with their upright lances. Then a sword-swinging fracas takes over, with one of the Russians’ retaliatory slashing perversely elongated and intercut with other battle scenes.

Eisenstein often wrote about unity of technique, and with this sound film, the tight audiovisual correspondences, unlike elsewhere in his work, attract more attention than the film’s central montage. The film’s orchestration, some of which sometimes determined Eisenstein’s cutting, ranges from a gathering march for the advancing enemy to a dirge over a tracking shot of war dead. One almost comical highlight occurs when the Teutonic harmonium player is pulled off his roost, cutting short the ominous chords that had been heralding his cohorts. It’s like a needle-off-the-record scrape, but for medieval warriors.

The Teutons are the most cartoonish element of Eisenstein’s film. They’re hidden behind single-slit helmets, headed by a horned leader, and prayed for by a rearguard camp of Lord Palpatine-worthy Catholics. Indeed, in a close shot of their galloping cavalry, the running-in-place motion of the horses and flags streaming in the background resembles a snatch of Disney animation. (Eisenstein, in fact, wrote extensively on Disney, and Prokofiev was impressed by their sync techniques.)

The movie closes with predictable triumph, but it is pointedly qualified by Nevsky underlining the need for vigilance. History bore that out with typical irony — first when Hitler and Stalin signed their pact the following year, then with the Nazi invasion (with the movie’s availability curtailed accordingly). Eisenstein, whose film actually shows Russian peasants emerging from holes in the ground to fight, received the Order of Lenin (as did Cherkasov), but outlived the coming war by only a few years.

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