The Calm Before the Storm: Science in the Interwar Years

The autumn of 1918 brought an end to the bloodiest conflict the world had ever witnessed, but the peace that followed proved illusory. In the streets of European capitals, demobilized soldiers struggled to readjust to civilian life while the industrial machinery that had churned out artillery shells and mustard gas now sat largely dormant. The great empires that had mobilized millions of men and bent entire economies to the war effort lay exhausted, their treasuries depleted, their populations traumatized. France had lost a generation of young men in the trenches of the Somme and Verdun; Britain emerged victorious but financially crippled, its empire stretched thin; the Austro-Hungarian and Ottoman Empires had collapsed entirely, leaving a patchwork of new nation-states to sort out the wreckage. And then there was Germany—a nation humiliated, stripped of territory, and burdened with blame for a war that, from the German perspective, it had neither started nor conclusively lost.

The Treaty of Versailles, signed in the Hall of Mirrors at the Palace of Versailles on June 28, 1919, imposed terms upon Germany that would reshape not only the map of Europe but the trajectory of science itself. Article 231, the so-called "war guilt clause," forced Germany to accept sole responsibility for the conflict. The reparations that followed—eventually set at 132 billion gold marks, though the final bill would not be paid until 2010—placed an crushing economic burden on the young Weimar Republic. Germany lost 13 percent of its territory, including the economically vital Alsace-Lorraine, the coal-rich Saarland, and substantial portions of Prussia. Most significantly from a military-scientific perspective, Germany was stripped of its colonies and forced to reduce its army to no more than 100,000 men. The Imperial German Navy, once the second largest in the world, was scuttled at Scapa Flow. Germany was forbidden from maintaining an air force entirely.

These restrictions, intended to prevent Germany from threatening its neighbors again, instead catalyzed one of the most remarkable technological undergrounds in history. The Treaty of Versailles had banned Germany from developing conventional weapons, but it said nothing about certain other fields of research—fields that would prove far more consequential than any artillery piece or battleship. German scientists and engineers, many of whom had cut their teeth on the war effort, now found themselves with powerful incentives to explore alternatives. The universities of Berlin, Munich, Göttingen, and Leipzig became crucibles of theoretical physics, chemistry, and engineering research that would eventually produce innovations far more destructive than anything the Treaty had sought to prohibit.

The quantum revolution, still reverberating through the scientific world in the 1920s, found fertile ground in German universities. Max Planck had first introduced the concept of energy quanta in 1900, arguing that energy could be emitted or absorbed only in discrete packets. Albert Einstein had built upon this foundation in 1905 with his paper on the photoelectric effect, demonstrating that light itself behaved as if composed of discrete particles—photons. Niels Bohr had applied quantum concepts to the structure of the atom in 1913, proposing that electrons orbited the nucleus in discrete energy levels. By the 1920s, a new generation of physicists was pushing these ideas further. Werner Heisenberg developed matrix mechanics in 1925, presenting quantum mechanics without reference to classical concepts like electron orbits. Erwin Schrödinger, working independently, formulated wave mechanics, showing that electrons could be described as probability waves. Paul Dirac unified these approaches and introduced the Dirac equation, which incorporated the principles of relativity and predicted the existence of antimatter. Max Born provided the probabilistic interpretation of the wave function, establishing that quantum mechanics was fundamentally about probabilities rather than certainties.

This was the intellectual atmosphere in which a young Robert Oppenheimer was learning physics. Born in New York City in 1904 to wealthy German-Jewish immigrants, Oppenheimer had attended Harvard University, where he completed his bachelor's degree in just three years, having excelled in both chemistry and physics. He then traveled to Europe for graduate study, spending time at the University of Göttingen under Max Born—a choice that placed him at the very heart of the quantum revolution. Göttingen in the 1920s was arguably the world's leading center for theoretical physics, home to a remarkable collection of talent that included not just Born but also David Hilbert, James Franck, and the brilliant young Werner Heisenberg. Oppenheimer thrived in this environment, impressing his colleagues with his extraordinary intellect and fierce intellectual ambition. He earned his doctorate in 1927, at age twenty-three, with a thesis on the quantum theory of the continuous X-ray spectrum. The following year he took up teaching positions at the University of California, Berkeley, and the California Institute of Technology, beginning the career that would eventually make him one of the most consequential—and controversial—figures of the twentieth century.

But if Oppenheimer represented the best of American theoretical physics in the 1920s, he also embodied its limitations. American universities, despite pockets of excellence, still lagged behind European institutions in fundamental research. The infrastructure for cutting-edge physics existed primarily in Germany, Britain, and to a growing extent, the Soviet Union. American physicists who wanted to stay at the frontier of their field often had little choice but to study abroad, typically in Europe. This would change over the following decades, driven by factors ranging from the rise of fascism to the outbreak of war itself, but in the interwar years, the flow of scientific talent still ran predominantly from America to Europe rather than the reverse.

The economic catastrophe that struck in 1929 would reshape these patterns in ways no one could have predicted. On October 24, Black Thursday, the American stock market crashed, setting off a chain reaction that would plunge the global economy into the Great Depression. By 1933, one quarter of the American workforce was unemployed; industrial production had fallen by half; banks were failing by the thousands. The devastation was not limited to the United States. Germany's fragile Weimar Republic, already struggling under the weight of reparations, was hit especially hard. German unemployment reached 6 million by 1932, roughly a third of the workforce. The middle class saw their savings wiped out by inflation; workers found themselves queuing at soup kitchens while factory chimneys stood cold. The political consequences were predictable: voters, desperate for solutions, turned to extremes. In 1933, Adolf Hitler became Chancellor of Germany.

The Depression's impact on scientific research was profound and varied across nations. In America, the federal government, under President Franklin Roosevelt's New Deal, began funneling money into scientific and public works projects. The Works Progress Administration funded the Federal Art Project, the Federal Writers' Project, and the National Youth Administration, while also supporting infrastructure projects that employed engineers and scientists. The National Institute of Standards and Technology, the Department of Agriculture's research stations, and various other federal agencies provided employment for scientists and engineers, though the scale of government scientific investment remained modest compared to what would come later. Private philanthropy, through foundations like the Rockefeller Foundation and the Carnegie Institution, stepped in to fill some gaps, funding fellowships and research grants that kept scientific work al