High muscle mass or bulk muscle is the incorrect term. I believe the term you were referring to is a lean physique or lean muscle mass. Without going into strength training vs weight training, high muscle mass is a net performance inhibitor, i.e. you can lift more but you cannot run well at all, your movement becomes sluggish and you get tired too fast due to the high energy requirements of your body, think Arnold Schwarzenegger here. This doesn't suit performance + endurance based endeavours, like being a soldier, very well. On the other hand lean muscle building enhances agility and endurance while trading lifting capacity, think Bruce Lee's physique here. This isn't optimal either. The optimal physique for a soldier is in between the two, think 100m sprinters. But there is one more question and that is of toning. Toning essentially means reducing fat while keeping high or lean muscle mass to either gain high definition and/or reduce weight. This results in the reduction of energy reserves for the body. This is good for a 100m sprinter but is not suited for a soldier. So what your really want in a soldier is a little bulked lean muscle with some fat reserves.
This is a physique built for pure strength based performance (muscle bulk + fat),
This is one built for show (muscle bulk + low fat),
This is another built purely for show (lean muscle + low fat),
This is built for strength + athletic performance with low body mass (strength based bulked lean muscle + low fat),
And this is how soldiers should be built i.e. strength + agility + energy reserves (strength based bulked lean muscle + fat),