Russell sent his statement to Einstein for approval, realizing that other scientists would be more willing to lend their name to something that Einstein had endorsed. While waiting for Einstein’s reply, Russell was on a flight from Rome to Paris when the pilot announced the news of Einstein’s death. Russell recalled: “I felt shattered, not only for the obvious reasons, but because I saw my plan falling through without his support. But, on my arrival at my Paris hotel, I found a letter from him agreeing to sign. … This was one of the last acts of his public life.” In the letter, Einstein declared: “I am gladly willing to sign your excellent statement.”

With Einstein’s dramatic, deathbed letter, Russell was able to garner nine other signatories for the statement—Max Born, Percy W. Bridgman, Leopold Infeld, Frederic Joliot-Curie, Herman J. Muller, Linus Pauling, Cecil F. Powell, Joseph Rotblat, and Hideki Yukawa. With the exception of Infeld (whose endorsement was crucial because he was from Communist Poland) and Rotblat, all of the signatories were Nobel Laureates.