The joint German and Soviet invasion of Poland in September 1939 resulted in World War II. During the following five years, 15 per cent of the Polish population perished and Poland was made to accommodate the mass extermination of the Jews in concentration camps. Germany immediately annexed western Poland, while Russia absorbed the eastern regions. Central Poland became the General Government, run as a separate administration by Nazi Germany. Lithuania was offered the disputed lands around Wino (Vilnius) and Slovakia was given a small disputed area on the Polish-Slovakian border, if they agreed to support the German-Soviet Union invasion. The Slovaks also agreed to allow Germany to use their territory as an assembly point for its troops. After Germany invaded the Soviet Union in June 1941, all Polish territory was ceded to the Third Reich and became part of the General Government. The Polish state had effectively ceased to exist, although a Polish government-in-exile had fled to France and subsequently London.