Knock 'em on their Axis!

I've been catching a few WWII propoganda documentaries from the 40s on TCM. Recently, I saw one where the narrator was discussing gunners on American airplanes. The short film showed footage of American gunners firing on German warplanes, and the narrator says, "That'll knock them on their Axis." Now that's gotta be one of the stupidest and yet funniest puns I've heard in a while. Don't ask me why I made a post about this, please...