The history of Poland can be divided into several periods: prehistory until 966 CE when Poland began forming under the Piast Dynasty and adopted Christianity; the Jagiellon Dynasty from 1385-1569 CE when Poland allied with Lithuania and experienced economic and cultural flourishing; the Polish-Lithuanian Commonwealth from 1569-1795 CE which was Poland's Golden Age when it expanded greatly; and partitions by Prussia, Russia, and Austria from 1795-1918 CE when Poland was erased from maps until it regained independence after World War I. Poland then experienced World War II occupation and communism until 1989 when it transitioned to a market economy and joined the EU and NATO.