From everything I've read he was pretty much like what you saw on screen. He got two purple hearts in Korea. While in the military he was a "scrounger" same as he was in the "Great Escape" and "The Americanisation of Emily"(my favorite). He was a pacifist, but had a sense of duty and served. From all accounts a great guy, it came across on screen.

Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats. H. L. Mencken