You might be overthinking it a bit. All men should be training for war all the time and this merely means continuous competence training that includes physical fitness. What you consider as competence depends on many things including your understanding and desire to step up and help in the hierarchy when called upon. There is room here for fitness from Tyler Durden to merely being healthy, in shape and able to carry a 100 pound military backpack on a daily grind for 20 miles or some such.