The Man Who Measured Uncertainty: Heisenberg, the Nazis, and the Bullet That Never Fired

It was the winter of 1944, and a young American spy named Moe Berg sat in a theater in Zürich, Switzerland, with a pistol hidden in his coat. He was there not for a diplomatic mission, but to make a decision that could alter the course of the war. His target: Werner Heisenberg, the man who gave the world the Uncertainty Principle, and possibly, Hitler’s atomic bomb.

This is the story of how science, espionage, and moral ambiguity collided in one of the most extraordinary assassination plots of the Second World War. It’s also a story that forces us to ask: when does a scientist become a threat? And who decides if a life is worth taking in the name of peace?

Werner Heisenberg was no ordinary physicist. By the 1920s, he had already become a central figure in the development of quantum mechanics. His work earned him the Nobel Prize in Physics in 1932 and the admiration of Einstein himself.

Heisenberg’s most famous contribution to science, the Uncertainty Principle, revolutionized our understanding of nature. At its core, it stated that certain pairs of physical properties, like a particle’s position and momentum, could never be simultaneously known with perfect precision. This wasn’t due to measurement limitations—it was a fundamental feature of the universe itself. It shattered the determinism of classical physics and laid the foundation for a radically probabilistic view of reality.

Einstein, though fascinated by Heisenberg’s brilliance, was deeply uneasy about this implication. He famously rejected quantum indeterminacy, remarking, “God does not play dice with the universe.” Yet the two men maintained mutual respect, even amid sharp philosophical disagreement.

When Hitler came to power, Heisenberg remained in Germany. Some scientists fled. Others resisted. He stayed and led Germany’s nuclear research program.

To the Allies, Heisenberg became a symbol of a terrifying possibility: that Nazi Germany might build an atomic bomb. Whether he was truly working toward that goal, or subtly sabotaging it, has remained a subject of debate ever since.

The fear wasn’t unfounded. In December 1938, German chemists Otto Hahn and Fritz Strassmann succeeded in splitting the uranium atom by bombarding it with neutrons, producing barium as a byproduct. The implications of this result were soon interpreted by Lise Meitner and her nephew Otto Frisch, who identified the process as nuclear fission. Their explanation, published in early 1939, confirmed that vast amounts of energy could be released by splitting atomic nuclei. For a brief moment, Nazi Germany was ahead in nuclear physics, setting off alarm bells among Allied scientists and prompting urgent action in the United States.

Meanwhile, on the other side of the Atlantic, Einstein’s own name would become entangled with the Allied response. In 1939, Hungarian physicists Leo Szilard and Edward Teller persuaded Einstein to sign a letter to President Roosevelt. The letter warned that Nazi Germany might be developing nuclear weapons and urged the U.S. to accelerate research, effectively launching what would become the Manhattan Project. Although Einstein played no role in the bomb’s actual development, his signature lent critical weight to the effort.

Thus, while Heisenberg and Einstein stood on opposite sides of the war, their scientific legacies, and moral uncertainties echoed in the fates of millions.

In 1944, as the war raged on, the Office of Strategic Services (OSS), the precursor to the CIA, recruited Moe Berg, a former Major League Baseball catcher turned polyglot and spy. His mission: attend a lecture Heisenberg was giving in Zürich and, if it became clear the German physicist was close to developing a bomb, eliminate him.

The plan was as cold as it was simple. Berg was to shoot Heisenberg during his walk back to the hotel, preferably in a quiet street. One shot, no trace.

“I would have shot him, gladly, if I was convinced he was building a bomb for the Nazis. But I wasn’t.” — attributed to Moe Berg in declassified OSS accounts.

Berg went to the lecture. He watched Heisenberg speak. He even got close enough to talk to him afterward. But he never pulled the trigger.

Why?

According to some accounts, Berg didn’t believe Heisenberg was close to building a bomb. Others suggest he couldn’t justify killing an unarmed scientist in neutral territory. Or perhaps, he glimpsed something in Heisenberg’s demeanor that spoke to doubt, or even quiet resistance.

For a fuller account, Thomas Powers’ book Heisenberg’s War offers a deep dive into the ambiguities of Heisenberg’s actions and intentions.

The assassination was called off. The war would end less than a year later without a German bomb.

But the questions linger.

Heisenberg’s wartime role is still fiercely debated. Was he genuinely trying to develop a bomb for Hitler? Was he stalling the project, hoping to run out the clock? Did he do just enough to keep himself alive, but not enough to make a difference?

And what of Moe Berg? Did he show moral courage in sparing a man’s life? Or did he take a risk that could have cost millions of others theirs?

The moral tension surrounding Heisenberg finds a striking contrast in the legacy of J. Robert Oppenheimer, the scientific director of the Manhattan Project. While Heisenberg worked in ambiguity, possibly resisting or merely failing, Oppenheimer led the team that successfully created the atomic bomb used against Hiroshima and Nagasaki.

Though Oppenheimer initially believed he was racing Hitler to the bomb, he was deeply shaken by its actual use on civilians. He later opposed the development of the hydrogen bomb and advocated for arms control stances that led to political exile during the McCarthy era. His haunting reflection, “Physicists have known sin,” marked a moment of reckoning for the scientific community.

Heisenberg and Oppenheimer were men of towering intellects trapped in the machinery of war—one perhaps guilty of doing too little, the other of doing too much. Their paths diverged, but their dilemmas mirrored each other: how much responsibility does a scientist bear for the application of his discoveries?

The assassination attempt on Heisenberg forces us to reflect not just on science and war, but on the limits of moral certainty. How do we judge choices made in times of great darkness, when even the brightest minds are cloaked in ambiguity?

Heisenberg’s legacy remains entangled with this story of shadows and silences. He gave the world the Uncertainty Principle—and lived a life that embodied it.

In a world still haunted by the intersection of scientific progress and political power, the Zürich episode remains a parable of its time: a moment when the fate of millions may have hung on one man's hesitation, and when knowledge itself became both weapon and shield. It reminds us that history often hinges not only on the actions we take—but also on those we refrain from.

“In the strict formulation of the law of causality... it is not the consequence that follows with necessity from the conditions, but the probability of an event.” — Werner Heisenberg, Physics and Philosophy (1958)