Einstein had briefly met Lindbergh a few years earlier in New York, so he wrote a note of introduction, which he included when he returned the signed letters to Szilárd. “I would like to ask you to do me a favor of receiving my friend Dr. Szilárd and think very carefully about what he will tell you,” Einstein wrote. “To one who is outside of science the matter he will bring up may seem fantastic. However, you will certainly become convinced that a possibility is presented here which has to be very carefully watched in the public interest.”
Lindbergh did not respond, so Szilárd wrote him a reminder letter on September 13. Two days later, he realized how clueless he and his colleagues had been when Lindbergh gave a nationwide radio address. It was a clarion call for isolationism. “The destiny of this country does not call for our involvement in European wars,” Lindbergh began. Interwoven were hints of his pro-German sympathies and even some anti-Semitic implications about Jewish ownership of the media. “We must ask who owns and influences the newspaper, the news picture, and the radio station,” Lindbergh said. “If our people know the truth, our country is not likely to enter the war.”
Szilárd’s next letter to Einstein stated the obvious. “Lindbergh is not our man,” he wrote.
The physicists’ other hope was Sachs, who had been given the formal letter to Roosevelt that Einstein signed. But Sachs was not able to find the opportunity to deliver it for almost two months.
By then, events had turned what had been an important letter into an urgent one. At the end of August 1939, the Nazis and Soviets stunned the world by signing a war-alliance pact and proceeded to carve up Poland. That prompted Britain and France to declare war.
Szilárd went to see Sachs in late September and was horrified to discover that he still had not been able to schedule an appointment with Roosevelt. “There is a distinct possibility Sachs will be of no use to us,” Szilárd wrote to Einstein. “Wigner and I have decided to accord him ten days’ grace.” Sachs barely made the deadline. On the afternoon of Wednesday, October 11, he was ushered into the Oval Office carrying Einstein’s letter, Szilárd’s memo, and an 800-word summary he had written on his own.
The president greeted him jovially: “Alex, what are you up to?”
Sachs worried that if he simply left Einstein’s letter and the other papers with Roosevelt, they might be glanced at and then pushed aside. The only reliable way to deliver them, he decided, was to read them aloud. Standing in front of the president’s desk, he read his summation of Einstein’s letter and parts of Szilárd’s memo.
“Alex, what you are after is to see that the Nazis don’t blow us up,” the president said.
“Precisely,” Sachs replied.
“This requires action,” Roosevelt declared to his assistant.
The following week, Einstein received a polite and formal thank-you letter from the president. “I have convened a board,” Roosevelt wrote, “to thoroughly investigate the possibilities of your suggestion regarding the element of uranium.” Still, the effort’s slow pace and meager funding prompted Szilárd and Einstein to compose a second letter urging the president to consider whether the American work was proceeding quickly enough.
Despite helping to spur Roosevelt into action, Einstein never worked directly on the bomb project. J. Edgar Hoover, the director of the FBI even back then, wrote a letter to General Sherman Miles, who initially organized the efforts, that described Einstein’s pacifist activities and suggested that he was a security risk. In the end, Einstein played only a small role in the Manhattan Project. He was asked by Vannevar Bush, one of the project’s scientific overseers, to help on a specific problem involving the separation of isotopes that shared chemical traits. Einstein was happy to comply. Drawing on his old expertise in osmosis and diffusion, he worked for two days on a process of gaseous diffusion in which uranium was converted into a gas and forced through filters.
The scientists who received Einstein’s report were impressed, and they discussed it with Bush. In order for Einstein to be more useful, they said, he should be given more information about how the isotope separation fit in with other parts of the bomb-making challenge. Bush refused. He knew that Einstein didn’t have and couldn’t get the necessary security clearance. “I wish very much that I could place the whole thing before him and take him fully into confidence,” Bush wrote, “but this is utterly impossible in view of the attitude of people here in Washington who have studied his whole history.”
Thus the scientist who had explained the need for a bomb-making project was considered too risky to be told about it.