Why did Einstein leave Germany when Hitler came to power?

Since the outbreak of WWI, Einstein was opposed to war, and used his notoriety to lecture against it during the 1920s and 1930s. With the rise of National Socialism in Germany in the early 1930s, Einstein’s position became difficult. Although he was a renewed German citizen, the two social movements which received his full support were Pacifism and Zionism. When Hitler came to power, Einstein decided to leave Germany for the United States in anticipation of Nazi persecution. He took a position at the Institute for Advanced Study in Princeton, New Jersey, while he continued public support of Pacifist and Zionist goals which made him the target of vicious attacks by anti-semitic and right-wing elements in Germany. In addition he was demanded as a speaker and wrote extensively on many topics, especially on peace. The growing fascism and anti-semiticism of Hitler’s regime convinced Einstein to sign his name to a letter written by American physicist Leo Szilard informing President Franklin D. Roosevelt of the possibility of an atomic bomb. This letter led the formation of the Manhattan Project for the world’s first nuclear weapons. Einstein himself did not participate in the project. We can only assume that this was due to ethical concerns.