Factual error: The Russians use a beeping "radio direction finder" to find the partisans by detecting a bug swallowed by the Mayor's son. In closeups the "direction finder" is seen to be an impedance meter (used for measuring AC resistance) - it's labeled "X=(down arrow) x (up arrow)(omega)". X is the standard abbreviation for impedance, omega means "ohms" (the unit of impedance/resistance), so the label says "impedance is lower dial times upper dial, in ohms". There is a piece of spiral twisted wire across the terminals of the impedance meter which would be useless for radio direction finding.
Visible crew/equipment: When Jeds drives into town to escape the Russians and hits a car, you can see the police and spectators farther down the street, where they had closed off the street for filming.
Factual error: When the Russian tank rolls up to the two gas pumps, the crew have a choice of regular gasoline (as indicated on the pump), or Good Gulf (a premium gasoline). And in fact one of the tankers tells the attendant, "Gasoline." The trouble is, all Soviet tanks, from the T-34 up through the T-80, have diesel engines for safety reasons.
Factual error: When the Soviet airborne troops first drop into Calumet in the first few scenes of the movie they are using US Army issue parachutes - MC1-1B.
Factual error: In the opening scene of the movie, the Soviet paratroopers are seen wearing smooth, black, leather parachute helmets. But Soviet Paratroopers have always worn tan, cloth parachute helmets with ridges that resembled tanker helmets.
Revealing mistake: In the beginning of the movie, when the teacher is shot, the impacts on his chest are out of sync with the actual gunfire. First, we see the soldier start shooting, but he fires several shots at point blank range before the bulletholes and blood appear on the teacher. Also, as the angle changes, the teacher falls backwards with more impacts appearing on his chest. The problem is, the soldier has already stopped shooting, and there is no other gunfire to be heard.
Other mistake: During the scene at the Arapaho National Forest sign, the soldier translates, "Roosevelt leading imperialist army and cowboys putting down a great peasant uprising... 35,000 dead... etc. etc." Yet the sign only reads, "Founded by Roosevelt under the forest service act of 1908 comprises acres of virgin timberland of..." No info of any battle is displayed.
Continuity mistake: After the helicopter attack where Toni and Robert are killed, the Russian helicopters land about forty feet apart, the officers get out and walk to meet each other at the halfway point. For the rest of the scene, they are right next to one of the helicopters.