Complex sentence: Later, Placzek was the only Czech at some leading positions in the Manhattan project, where he worked from 1943-1946 as a member of the British Mission D. C. Fakley: "The British Mission".
Split into simpler sentences: Later, Placzek was the only Czech at some leading positions of the Manhattan project. He worked there from 1943-1946 as a member of the British Mission D. C. Fakley: "The British Mission".