Today I read Steinbeck's short novel The Moon Is Down, which is about a small town that gets captured by an invading army (obviously the Germans, though their country isn't named) and embarks on a campaign of quiet resistance.
This book was written as an explicit piece of propaganda! Steinbeck was working with the OSS, the precursor to the CIA, when he wrote it, and the book quickly spread through various resistance movements in Denmark, Norway, the Netherlands, and France, who translated it and distributed it at great personal cost. The book became a huge hit, even during the war, and afterwards, when it was published in legal editions, it sold out pretty large print runs in all those countries.
Meanwhile, at home, the US literary critics were debating whether it was worthwhile as a piece of propaganda or not. The problem, some critics claimed, was that the Steinbeck had given a too-kind and too-romantic picture of the invaders. He portrays them as a bunch of average guys who're forced to do a dirty job. They don't want to shoot innocent people. They don't want to commit genocide. They don't even want to be rude. They're thoroughly ordinary folks. And the claim was that by downplaying the horrors of life under Nazi rule, he would discourage resistance.
I don't know what to say to that, but the book's popularity kind of speaks for itself. Actually, according to the introduction to the book, nobody realized how popular the book had been during the occupation until about fifty years afterward, when somebody collected all these stories, and they realized the sheer number of illegal copies that had circulated.
It's a very interesting thing, though, this intersection of art and ideology. And there is something very compelling about the idea that truthfulness and subtlety make for the most compelling propaganda.