Be a bit careful about who you declare war on, and read the quest descriptions carefully. Don't do what I did during my first attempt and declare war at the wrong guy
I ended up with with a war that I could not possibly win. There is a set order in which you are supposed to capture the major sites, and if you try to do it out of order, the game will punish you harshly for it. The game might look like a Total War-like game, and it might initially try to fool you into believing that it is, but in the end, it's actually relatively linear. You have a few paths to chose from, but once you've picked a path, don't stray from it.