In my story, I know that there needs to be a war with a big scary villain, etc, etc. However, I can't think of anything that would need a war. The trope about land makes me exhausted just to think about, like a history class all over. There have to be other reasons for war, but I can't think of any. Anyways, I would appreciate any ideas anyone has.
When boiled down, there's basically four to five sources for having a war. Wealth - a richer country waging war on a poorer one to take control of their resources, or someone calling in wealthier allies to overrun another; your aforementioned land; freedom - fighting to throw off another's control, or starting a war between their own people; and lies - aka "there's weapons of mass destruction in Iraq". Hope that can help a bit!
One thing to note on war is that all war is politically motivated (war is politics in its most destructive form). Its a tool to push policy.
Hope this helps.