Complex sentence: He left France in 1939 and emigrated to America in 1940 (his Jewish background made it impossible for him to return to his native country until after the Liberation); he secured a teaching post at Mills College in Oakland, California.
Split into simpler sentences: He left France in 1939 and emigrated to America in 1940 (his Jewish background made it impossible for him to return to his native country until after its Liberation). He secured a teaching post at Mills College in Oakland, California.