Skynet, as this war just broke out, had about that many T 800s, these ones where fitted with a time machine, like a Mimic, from the movie Edge of Tomorrow. So they can’t lose. But their are various other things in the world that they don’t have, plus the unexplored regions. The world is now just a bunch of machine cities. The resistance forces have gone underground. The people of the 20th century that brought them here, through nuclear bombs between triads, got them this far. Human population is thin now, but we are surviving. This is the real thing, so things are really slow. Imagine, just some underground bunkers and few hand guns, that meager.