Anti-Nazi films were rare even by 1939, this film was banned and censored in parts of the US even as armies prepared for war in Europe. So this is a significant film though not that good a one.
It follows a group of anti-Nazis including Alan Ladd, Roland Drew, Greta Granstedt and Steffi Duna. They are printing pamphlets and spreading dissent, all the while scared of betrayal and being caught by the brutal SS. A complication is that one of their number, Hans von Twardoski, is a member of the SS but wants out before liquor consumed in a Nazi booze-up loosens his tongue...
The propaganda is laid on heavy, as heavy as a Tiger tank. For some reason the actors speak English with a vague German accent interspersed with a few actual German words like Ja and Auf wiedersehen. At times it is a bit Allo Allo, though darker. At times very dark indeed.