People always think size means everything, never think about logistics or simple things like food, medical supplies, ammunition, getting it to this "huge army".
Having a large population doesn't mean you have a big army or even when forced to fight, have them all using adequate gear or have the right training in time.
Nobody knows what a full scale war will be like in the modern era, with more concern about collateral damage etc, will anyone be ballsy enough to use their nuclear arsenal? If anything, it would be false flag, you'd have to be pretty stupid to do it from the country you are trying to help. You can guess but when it comes down to it, we don't know what nations will do if desperate enough today.
Or will we go back to our old ways? Screw the civilians, they are just in the way, just fire at anything that isn't us and lets see if we're still standing tomorrow. That's why the conflict in the middle east won't end any time soon, a cowardly(yet... it's clever) enemy who hides amongst civilians, sneak attacks, hidden explosives, etc.
If we had the same disregard for innocent life, that part of the world would be a lot different now.