Fact-based movie?

It was a Vonnegut novel, completely fictional. He wrote it as though it were a translation of an actual man's memoirs (what Campbell is typing throughout), and that he only served as the translator from German to English. This, however, is just a literary device. This story is pure Vonnegut, and, in my opinion, it's Vonnegut at his best.

My digital cable program said that the movie was based on the "True story of Howard W. Campbell Jr. , an American that spied on Nazi Germany during WWII"
I scoured the Internet to find out about this "true story", but found that my cable program was wrong, the story was fictional. I hate getting false information.
The character Howard W. Campbell DID appear in the novel Slaughterhouse Five.

Don't trust everything you read on wikipedia. Any good scholar will tell you that half the information on that site is false. As for Kurt Vonnegut and Howard, Howard is writing as a real man in history but he is purely fiction. It is, as stated above, a genius literary technique. One that is captured in the book perfectly and pretty well in the movie.

Every writer is a frustrated actor who recites his lines in the hidden auditorium of his skull.

Even if we take the wikipedia article to be accurate, it says nothing about Joyce being a British spy working in Germany. He moved to Germany because he was into fascism, and he'd been in British fascist groups. He was an unrepentant anti-Semite. Maybe he was the inspiration in the sense that he was a non-German broadcasting propaganda for the Nazis, but the point of the book and film is that Campbell doesn't care about fascism or racism or governments or anything but his wife.

Is it possible that the Campbell character was inspired by American poet Ezra Pound? According to http://en.wikipedia.org/wiki/Ezra_Pound, the renowned literary man did a few anti semitic radio broadcasts in Italy and after the war had to stand trial in the United States for high treason.

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