The article analyzes ethno-political processes before and during the First World War. It is noted that all parties at war attempted to use ethnic factor against their rivals. Simultaneously, some powers repressed ethnic minorities, if those minorities were considered not loyal to corresponding authority. The article focuses at repressions by Austro-Hungarian authorities against pro-Russian movement in Eastern Galicia, as well as at the genocide of Armenians in the Ottoman Empire. The article notes that ethnic cleansings and genocide during the First World War are similar to nazi crimes during the Second World War.