What does the Army have in terms of investigations? I seen they have Criminal Investigations Special Agent (31D), but is that all? I know the AF has SF Investigations, and another more private one called OSI, where no one knows your rank, what you do, or anything. You never wear your uniform in OSI, it's basically like your an FBI agent. Is it hard to get into 31D? Anyone here a 31D or have a friend that's one? Any info would be great, thanks!