Ukraine after the Russian Revolution
Various factions fought over Ukrainian territory after the collapse of the Russian Empire following the Russian Revolution of 1917 and after the First World War ended in 1918, resulting in the collapse of Austria-Hungary, which had ruled Ukrainian Galicia. The crumbling of the empires had a great effect on the Ukrainian nationalist movement, and in a short period of four years a number of Ukrainian governments sprang up.
Source: Wikipedia — Ukraine after the Russian Revolution (CC BY-SA 4.0)