Moscow is presented as a point of contact between Soviet science and the wartime atomic project: from there, physicist Peter Kapitza invited Niels Bohr to join Russian colleagues, prompting Bohr to imagine an exchange of atomic knowledge for a more open Soviet Union. The city’s significance lies less in a depicted physical setting than in the diplomatic possibility attached to that invitation—whether scientific relations could displace secrecy and suspicion before the bomb made them harder to overcome.

A letter from Moscow

In the early spring of 1944, a long-delayed letter reached Bohr from his former student Peter Kapitza, writing from Moscow. Kapitza warmly invited Bohr to settle there with his family, assuring him that they would have shelter and the conditions needed to continue scientific work. He also conveyed greetings from Russian physicists Bohr knew, suggesting that they would welcome him into their scientific community. The letter made Moscow more than a distant wartime location: it appeared as a possible site of renewed personal and professional contact across the alliance.

Bohr’s proposal for openness

Bohr regarded Kapitza’s invitation as a promising opening and hoped that Franklin D. Roosevelt and Winston Churchill would permit him to accept it. As J. Robert Oppenheimer later explained to colleagues, Bohr wanted to use his scientific connections to propose an exchange: the United States and the United Kingdom would share atomic knowledge if the Soviet Union agreed to open itself and join an open international order. The proposal linked scientific collaboration to political transparency; for Bohr, knowledge could not safely remain a guarded national possession while every country feared that another was secretly building atomic weapons.

Bohr also read the letter as evidence that Soviet physicists might already know something about the British-American atomic program. Keeping them excluded, he feared, would foster the suspicion that the bomb was being developed against the Soviet Union. Oppenheimer shared the underlying concern, though he remained circumspect during the war because he knew he was under surveillance. Moscow thus figures in the account through a tension between the practical reach of scientific relationships and the limits imposed on them by military secrecy.

The wider question of Soviet participation

The possibility of Soviet involvement also surfaced in wartime discussions about ending the war with Japan. On June 18, 1945, John J. McCloy told Harry S. Truman that Japan’s military position was so weak that the administration should consider whether Soviet assistance was needed. McCloy urged political steps toward surrender before deciding on an invasion or atomic-bomb use. This was not a negotiation depicted in Moscow, but it shows how the Soviet Union’s role remained a live question in American policy as the war neared its end.

The contrast is significant: Bohr’s proposal treated contact and shared knowledge as a way to build confidence before the bomb became an accomplished fact, while military deliberations continued to weigh Soviet participation in the immediate conduct of the war. Moscow’s place in the narrative is therefore largely prospective. It marks the possibility of a scientific and political opening that Bohr believed might prevent the postwar nuclear rivalry, even as the approaching use of the weapon threatened to narrow that possibility.