I'm writing a story but it wouldn't make sense without context about the world it takes place in. What questions should I ask and where can I ask them?

I've written over 30,000 words about my characters and their various relationships, but I don't think I can proceed any further without a deeper understanding of the world they live in. The main plot of my story will take place during a war, but I have no idea what the war is about, who the belligerents are, and what the history of the war is. I also don't know anything about the history of the world my story takes place in. I realize I should probably have figured all these things out before I started writing, but I didn't, so now I'm trying to rectify the problem. What information do I need about the world my story is taking place in to proceed with writing it, and where can I go to find the answers to these questions?<br><br>&#x200B;