The scene at the Reichstag in 1945 when the Soviet flag is planted on the roof is based on a real incident. The soldier helping the one holding the flag was indeed wearing several watches, but the captain taking the photo failed to see it. As newspapers around the world published the photo, Stalin became angry at the implications of looting by the Red Army so the scene was staged and photographed again. Today both versions exist but there is no clear evidence of who the soldier holding the flag is.
The film was banned in Russia shortly after receiving the screening license.
The novel "Child 44", by Tom Rob Smith, was broadly inspired by the crimes of the real-life Russian serial killer, Andrei Chikatillo. Smith acknowledged this, but pointed out that those crimes were committed in a later period of Russian history - the earliest known murder was in 1966, long after Stalin's death, and continued until the last days of Communism in Russia. They were the subject of a TV movie, "Citizen X".
The first cut of the film was around five and a half hours long.