Joseph Rotblat (4 November 1908 – 31 August 2005) was born in Warsaw, Poland.
After the first World War he worked as an electrician. He won a place in the physics department of the Free University of Poland, where he discovered that neutrons were emitted during the fission process.
Rotblat realized his research could be used to help develop an atomic bomb. He continued his research to act as a deterrent against Nazi Germany should they develop a atomic bomb. He went on to work for the Manhattan project and was the only physicist to leave the Manhattan Project on the grounds of conscience.
He shared, with the Pugwash Conferences on Science and World Affairs, the 1995 Nobel Peace Prize for efforts toward nuclear disarmament.
Sources:
http://www.atomicheritage.org/profile/joseph-rotblat
https://en.wikipedia.org/wiki/Joseph_Rotblat