Germany invaded Poland and captured the Free City of Danzig on 1 September 1939 , beginning World War II in Europe . Honouring their treaty obligations , Britain and France declared war on Germany two days later . Poland fell quickly , as the Soviet Union attacked from the east on 17 September . Reinhard Heydrich , chief of the '' Sicherheitspolizei '' ( SiPo ; Security Police ) and '' Sicherheitsdienst '' ( SD ; Security Service ) , ordered on 21 September that Polish Jews should be rounded up and concentrated into cities with good rail links . Initially the intention was to deport them further east , or possibly to Madagascar . Using lists prepared in advance , some 65,000 Polish intelligentsia , noblemen , clergy , and teachers were killed by the end of 1939 in an attempt to destroy Poland 's identity as a nation . Soviet forces advanced into Finland in the Winter War , and German forces saw action at sea . But little other activity occurred until May , so the period became known as the " Phoney War "
lists prepared in advance
Operation Tannenberg
Nazi Germany