Factual error: When Rick is talking about the German guns shelling near Paris, he describes them as 77's (non-existent) - likely meant the famous 88's used as anti-aircraft and tanks as well as for wheeled guns. [The line was originally "88s" but was changed at the request of the War Dept. so as to not tip the German's hands that we knew about the 88s.]
Factual error: The opening credits name S.Z. Sakall as S.K Sakall, and the globe of the world which follows the credits has the USSR listed as the Union of Socialist Soviet Republics. The original name of the USSR in Russian was "Soyuz Sovetskikh Sotsialisticheskikh Respublik" which translates as Union of Soviet Socialist Republics.