This sounds insane. My hobby is medium distance hiking in (say, 250 km/155 mi na week) in the Scandinavian Arctic, so I have to carry all my food. I'm a fan of ultralight hiking, so my whole summer baggage weights around 10 kg/20 lbs excluding water. I invested some money in lighter equipment, yes, but most of my weight savings is stuff I simply do not take with me, or things that serve in multiple roles (eg. my hiking poles double as tent poles). A common piece of advice in the ultralight community is "don't pack your fears" – take only what you know you're gonna need, avoid redundancy (and be careful not to lose your crap), and consider what you can do without (an example: you don't really need a big ass knife).
Anyway, with 10 kg pack a trip is extremely physically challenging, but overall pleasant. I can actually enjoy the view, as opposed to just wanting to throw my backpack on the ground (I didn't get to my low weight immediately, I used to carry much more before).
Hiking like I do, but with 100 lbs of gear sounds like a nightmare. A soldier may not care about the views, but he should watch out for people who are trying to kill him. If my experience translates at all, the weight is interfering with that goal.