The plot is based on the concept of a group of Nazis building a colony on the moon in 1945 and then remaining there with their outdated technology, waiting for the right time to strike.
And like I said, its a comedy.
In the same vein that Charlie Chaplin's "The Great Dictator" was a comedy.
Having seen the film I give it 3 and half stars out of 5. The trailer is below. You can stream the full film on http://www.movie2k.to/index.php and doing a search for "Iron Sky".