“In the course of the last four months it has been made probable…that it may become possible to set up a nuclear chain reaction in a large mass of uranium. Now it appears almost certain that this could be achieved in the immediate future.
This new phenomenon would also lead to the construction of bombs, and it is conceivable- though much less certain- that extremely powerful bombs of a new type may thus be constructed.”
On August 2, 1939, Hungarian physicist Leo Szilard sent this warning to President Franklin D. Roosevelt in a letter signed by none other than Albert Einstein.
Saturday marked the 75th anniversary of the Einstein-Szilard letter. And yet the dangers Szilard warned against in his letter 75 years ago still loom over society: now in the form of over ten thousand nuclear warheads spread across the globe. In revisiting the writings of Leo Szilard, it is chilling to note how many of his words, drafted in a different era, still apply to the world today. Much has changed since the Einstein-Szilard letter arrived on the doorstep of President Roosevelt 75 years ago; leadership has risen and fallen, technology has progressed in leaps and bounds, wars and revolutions have sparked and faded. Yet still the threat of nuclear war remains. Worse, that threat has proliferated.
Scientists have always played a complex role with regard to nuclear weapons. While nuclear physicists were the individuals immediately responsible for the weapons’ design and creation, the same nuclear physicists were often the individuals protesting the government’s use of these weapons and warning against the inevitability of their eventual proliferation. Such was the case with Leo Szilard, a man vital to the atomic bomb’s construction.
Among Szilard’s numerous scientific innovations, he was the first to conceptualize and later successfully test a controlled uranium nuclear chain reaction, a chemical process integral to creating an atomic explosion. It was this discovery that compelled him to draft the Einstein-Szilard letter on August 2, 1939, cautioning the President on the new implications for nuclear weapons and urging Roosevelt to act. Roosevelt took the letter to heart; his choice of action was to charge Szilard and a team of other scientists with the Manhattan Project, a project with the ultimate goal of creating an atomic bomb for the United States.
However, when we remember Szilard today, it is not solely for his role as a physicist in constructing the first atomic bomb. It is also for his role as an advocate, in championing messages of peace and disarmament to a world that seemed set on war and destruction. In this way, Szilard embodies the kind of scientists who have fought and continue to fight for a responsible and ethical approach towards nuclear weapons. Today, organizations such as the Union of Concerned Scientists, Scientists for Global Responsibility, and the Bulletin of the Atomic Scientists continue to warn of the dangers that nuclear weapons pose to society. Where Szilard first cautioned against nuclear threats from Germany and later from the Soviet Union, scientists today point towards a multitude of possible disaster scenarios: tensions in South Asia and the Korean peninsula resulting in nuclear exchanges, non-state actors obtaining nuclear weapons through theft, and nuclear terrorism in the Middle East are just a handful of the frightening possibilities.
The Einstein-Szilard letter may have been the beginning, but Leo Szilard continued to write extensively on the topic long after the Manhattan Project concluded. He wrote against the use and spread of nuclear weapons following the destruction of Hiroshima and Nagasaki, protesting their usefulness during the Cold War. In Szilard’s 1961 speech “Are We on the Road To War”, he stated his argument succinctly:
“If we intend to drop our bombs on Russia in case of war and expect Russia
to drop her bombs on us, so that both countries would be wholly devastated,
then our threat to drop bombs on Russia is tantamount to a threat of murder and
It is no longer 1961, but the irrational dual threat of murder and suicide lingers. Although we no longer teeter on the brink of a Cold War, the dangers of nuclear proliferation still pose a real threat.
On this 75th anniversary of the Einstein-Szilard letter, we would like to commemorate Leo Szilard, Albert Einstein, Robert Oppenheimer, and all the atomic scientists who condemned nuclear weapons as unethical and impractical. We would like to thank the many scientists today who still demand greater nonproliferation efforts, collaborate on possibilities for disarmament, and write on the dangers of nuclear weapons. Finally, we would like to keep in mind that although many years have passed since 1939, there is still much work to be done to create a world safe from the threat of nuclear destruction.