If you are a combat athlete you need to have a wide variety of attributes. Mastering, or at least getting a good handle on those attributes, can literally be a matter of life or death. So having a conditioning program that gives the participants a wide spectrum of skills and attributes is going to make them more adaptable and hopefully increase their chances for survival.
Up until a handful of years ago military PT (Physical Training) centered around push ups, pull ups, sit ups and lots and lots of running. Today there are different options to get our warriors ready for combat and one of them is CrossFit. Check out this article that explains the reasons why the Army choose CrossFit and how they studied injury rates to make sure it was safe alternative to their existing program.