I've been fascinated by conflicts like the Polish-Soviet War of 1919-1920 and the earlier Polish-Ukrainian War of 1918-1919. I'm curious if anyone here knows of historic texts that discuss the political and military situations surrounding these conflicts and how they played into the national identities of Eastern Europe
Timothy Snyder's Bloodlands is an excellent work, looking at Eastern Europe in the interwar and second world war periods. For books focusing on the Russo-Polish war and the Ukrainian struggle for independence, I'm afraid I can't help you there. Norman Davies God's Playground is a history of Poland, so I'm sure that those conflicts would be mentioned and examined, especially the Russo-Polish War.