During training in GITMO for the MP's who "guard" the detainees apparently a drill was run using a soldier the MP "rapid reaction force" did not know. They kicked and beat the living shit out of him. Literally.

Spc. Sean D. Baker, 38, was assaulted in January 2003 after he volunteered to wear an orange jumpsuit and portray an uncooperative detainee. Baker said the MPs, who were told that he was an unruly detainee who had assaulted an American sergeant, inflicted a beating that resulted in a traumatic brain injury.
...
The Pentagon initially said that Baker's hospitalization following the training incident was not related to the beating. Later, officials conceded that he was treated for injuries suffered when a five-man MP "internal reaction force" choked him, slammed his head several times against a concrete floor and sprayed him with pepper gas.
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As he was being choked and beaten, Baker said, he screamed a code word, "red," and shouted: "I'm a U.S. soldier! I'm a U.S. soldier!" He said the beating continued until the jumpsuit was yanked down during the struggle, revealing his military uniform.

"While it is unfortunate that Spc. Baker was injured, the standards of professionalism we expect of our soldiers mandate that our training be as realistic as possible," the spokesman said. my emphasis