between the world wars, Poland included the "Kresy", parts of modern-day Lithuania, Belarus, and Ukraine. In 1940, Following the Soviet invasion of Poland, several hundred thousand Poles were arrested and imprisoned; over a million Poles were deported to Siberia and Kazakhstan in 1940.
Archivally complex
records held in numerous lands (Poland, Russia, Lithuania, Belarus, Ukraine, Iran, various countries in Africa, UK, ...); key records still not available due to access restriction; some records destroyed at the time; complex provenance of other records; many (perhaps 200,000) surviving Poles settled in the UK, not in Poland, after the war.
