Eisenstein and Prokofiev made one of the great war films. But how did they manage to keep Stalin happy?

An otherwise barren landscape is littered with helmets, shields and bones. Birds rest upon a ribcage. An arrow embeds the earth between human skulls. A Mongolian platoon approaches and is quickly met by a broad shouldered man in a white tunic. With his hands on his hips and his golden curls billowing, he declares himself in a deep voice, simply, “Alexander”.

So opens the epic 1938 film Alexander Nevsky, tagged variously as “100% propaganda” and “the first music video”. Its driving orchestral score underpins the 13th-century victory of the Novgorod warrior who shields his fellow Russians from invading Germans. The project united two of Russia’s key artistic minds, director Sergei Eisenstein and composer Sergei Prokofiev, and became a massive cinematic hit. The score’s subsequent life as a cantata ensured its legacy in the concert hall.

Yet its success hid the terrifying struggle Soviet artists faced against the state. The film not only became a political football, kicked on and off the screen according to Russia’s volatile dealings with Germany, but marked Prokofiev and Eisenstein’s inevitable absorption into socialist...