On October 17th 1933, Albert Einstein arrived in the United States to stay. He and his wife had been returning to Europe by ship in the Spring, when they heard that Germany had passed the Enabling Act that gave Hitler dictatorial powers. They decided it would be unwise and unsafe to return to Berlin as planned, but went instead to Belgium, and six months later to the United States.
Their precaution was justified, in that they learned that the Nazis had raided their cottage, confiscated and sold his sailboat, and later converted his cottage into a Hitler Youth camp. Einstein accepted an offer from the Institute for Advanced Study, a body that became a haven for refugees fleeing Nazi Germany. Other big-name US universities had minimal or zero Jewish faculty or students at that time.
Einstein’s decision to make America his new home - he became a citizen in 1940 - had deep consequences. A group of Hungarian scientists tried to warn Washington that an atomic bomb might be possible, and might be put together by the Nazis and used against their enemies. Their warning was not heeded, so they tried a more serious effort. Leó Szilárd and Eugene Wigner went to see Einstein to explain the possibility. Einstein, already a known pacifist, had shown that a small amount of matter could be converted to vast quantities of energy, but had never envisaged a chain reaction, or had ever considered the possibility of nuclear energy being harnessed for weaponry. Nonetheless, he agreed to join them, along with Edward Teller, in alerting the White House.
Einstein joined with Szilárd in writing a letter to President Roosevelt, and such was his prestige as a scientific genius that the letter was put into Roosevelt’s hands. He met with Roosevelt, and historians suggest it was that letter and the meetings that led the President to initiate the Manhattan Project, committing immense financial and scientific resources to develop an atomic bomb before Nazi Germany might do so.
Einstein did not participate in the project that saw America successfully make two types of nuclear bomb, and use them to end the war against Japan with far fewer American or Japanese casualties than an invasion would have entailed. He did not comment at the time, but did express regret that the bombs had been used, and had unleashed a new and deadly era of warfare upon the world.
Einstein wrote to Linus Pauling, his old friend, in 1954, a year before his own death. He said, "I made one great mistake in my life - when I signed the letter to President Roosevelt recommending that atom bombs be made; but there was some justification—the danger that the Germans would make them."
He was certainly correct about the last part. The Germans were producing new weapons that took warfare to new dimensions. They produced the V1, the world’s first cruise missile. The launched the V2, the first ballistic missile. And they made the Me262, the first operational jet fighter. They had skilled scientists, and might have produced the atomic bomb. Had they done so, the consequences would have been catastrophic for the world. Einstein’s letter was, in retrospect, a wise precaution.