 Einstein was offered a position at the Institute for Advanced Study at Princeton, New Jersey,
an affiliation that lasted until his death in 1955.In the summer of 1939, a few months before the beginning of World War II, Einstein was persuaded to write a letter to president Franklin D. Roosevelt and warn him that Nazi Germany might be developing an atomic bomb.Einstein helped strengthen the letter, and he recommended the U.S. begin uranium enrichment and nuclear research.