Simplify the following text for a Grade 7 native English-speaking person.
Original: Hurwicz , who had graduated from Warsaw University in 1938 , at the time of Nazi invasion on Poland was in London , moved to Switzerland then to Portugal and finally in 1940 he emigrated to the United States .
Simplified: Hurwicz was forced to move to Switzerland , then to Portugal and finally in 1940 he moved to the United States .