He felt he had an obligation to help science in Poland recover from the ravages of the Second World War. He served as president of the Polish Physical Society between 1955 and 1957. In the staunchly anti-communist climate of the time, many in the Canadian government and media feared that working in a communist country he would betray nuclear weapons secrets. He was stripped of his Canadian citizenship and was widely denounced as a traitor. In actuality, Infeld's field was the theory of relativity —not directly linked to nuclear weapons research. After Infeld's return to Poland, he requested a leave of absence from the University of Toronto. His request was denied, and Infeld resigned his post. In 1995 the University of Toronto made amends and granted Infeld the posthumous title of professor emeritus. Upon his return to Poland, Infeld became a professor at the University of Warsaw, a post he held until his death.