"I can't think of any real war or major fighting that happened strictly because..." That's the point. :) You don't fight over the river per se because it's imp

"I can't think of any real war or major fighting that happened strictly because..." That's the point. :) You don't fight over the river per se because it's impossible. They fought over all the land right up to the river. Presumably the riverfront on the other side is just as valuable, and total control over its water would make it more so. So why not take both sides? Because the land immediately after the river is indefensible. It's indefensible because your back is to a river. You can fight and win a war over land but you can't normally take a river. You don't even think about it. Thus you don't "fight a war" over it, even though the land you say you're really fighting for would be useless without it.