CHAPTER FIVE

WAR

WORLD WAR II NEWSREEL

NARRATOR: “Poland, September, 1939, the German Wehrmacht begins its ruthless march of conquest and sets the stage for World War II.”

Rejecting the trench warfare and static defenses of World War I, the German war machine adopted a strategy it called “blitzkrieg,” lightning warfare. After smashing through Poland’s border defenses, the first wave, made up of German tanks supported by Luftwaffe bombers and fighters, encircled Polish troops. The second wave of motorized infantry followed, securing their gains. Then the regular infantry took over, releasing the motorized infantry to race after the tanks that had already rolled deeper into Polish territory. It took the Wehrmacht just three weeks to defeat Poland’s smaller and poorly equipped forces.

In a preview of the atrocities to come, the Germans bombed the city of Warsaw and strafed civilian refugees as they clogged the roads trying to escape. Nazi paramilitary death squads executed 20,000 Poles, most of them Jews and intellectuals, and buried them in mass graves. In all, more than 150,000 Polish civilians were killed. 47 Two days after the invasion, England and France sided with Poland, launching what would become the bloodiest war in history.

To celebrate his army’s stunning victory, the Führer delivered a speech in which he extended both an olive branch and an iron fist. He vowed that Germany had “no war aims against Britain and France,” but at the same time threatened any nation that dared oppose it saying, “We will employ a weapon with which we could not be attacked.” 48 Hitler’s threat set off alarms throughout the continent and filled newspapers with speculation about a secret weapon, a Nazi “death ray.” 49

1940-05-13 CBS RADIO NEWS: ELMER DAVIS AND THE NEWS

On the fourth day of the invasions of the low countries the Germans are ahead of schedule, according to Berlin, but as in Norway and Poland, their advances have been made by fast armored divisions, and the mass of troops has not yet caught up with them.

“THE FIGHTING TODAY DECIDES the fate of the German nation for the next 1,000 years,” Adolf Hitler proclaimed. Meanwhile, as German armies rolled across Europe, intelligence pointing to a German bomb program continued to trickle in. Allied analysts monitoring Hitler’s public speeches took special note of his repeated boasts of a “wunderwaffe,” a wonder weapon. Sources reported that the uranium mine in the Czech Sudetenland, now under German control, had stopped exporting uranium and that the Germans were experimenting with a nuclear reactor at a research laboratory outside Berlin. “Every German scientist in this field—physicists, chemists and engineers,” The New York Times reported, “have been ordered to drop all other researches and devote themselves to this work alone.” 50 From the French resistance came word that German scientists had seized an American cyclotron at the College de France in Paris. The Germans had none of their own, and they desperately needed one to take the precise atomic measurements necessary for an atomic bomb.

Each bit of information added another piece to the giant intelligence puzzle Allied analysts were assembling, but there were still too few to get a clear picture of Germany’s intentions.

In 1940, despite the warning signs, British scientists held to the conventional wisdom that the scarcity of U235 atoms in a pound of uranium made building an atom bomb impossible. A “critical mass,” the mass of U235 atoms sufficient to sustain a nuclear chain reaction, would require many tons of uranium. The bomb would be far too large to carry in an airplane. So said the conventional wisdom.

But what if the conventional wisdom was wrong? Early in 1940 two physicists, Otto Frisch and Rudolf Peierls, victims of Nazi anti-Semitism now working at Birmingham University in England, began pondering that question. What if Heisenberg and colleagues could separate the rare U235 atoms from the natural uranium and assemble them into a mass of pure U235? If they did, they wouldn’t need to slow the neutrons down so they could sneak past the U238 guards. What if he bombarded the U235 atoms with fast-moving neutrons instead? No one, at least no one on the Allied side, had considered those possibilities.

On a lark, Frisch and Peierls decided to run the numbers and were shocked by what they discovered. The critical mass necessary to build a bomb was no longer measured in tons. It would be just a few pounds! “At that point,” says Frisch, “we stared at each other and realized that an atomic bomb might after all be possible.” 51

Following their discovery, conventional wisdom did an about face. A committee of British scientists set up to study nuclear fission concluded that a U235 bomb was “practicable and likely to lead to decisive results in the war.” 52 It recommended that the bomb be given the “highest priority.”

After some delays, those findings eventually made their way across the Atlantic where they reached the desk of President Franklin Roosevelt. The United States was not involved in the war, and the White House had shown little interest in funding nuclear research prior to that. But, in October 1941, the President finally authorized preliminary research on building an atom bomb. 53

LAWMAKERS IN WASHINGTON MAY NOT have paid much attention to nuclear fission, but America’s universities had. At U.C. Berkeley, Glenn Seaborg, the ill-fated physicist who had kicked himself for failing to recognize nuclear fission, was back in his laboratory bombarding uranium atoms in a cyclotron. 54 This time, his persistence paid off. In February 1941, Allied efforts to harness the energy of the atom took a giant leap forward when his experiments produced an atom that had never existed in nature, a new, man-made atom. He called it plutonium. Plutonium was a byproduct of nuclear fission. If scientists could build a machine that sustained a nuclear chain reaction, they could theoretically produce large quantities of plutonium. A plutonium bomb would have great advantages over U235. It would require a smaller critical mass of atoms than U235, so less processing. But more importantly, it could be separated from other uranium atoms using existing chemical procedures. No new separation technology would have to be invented.

The plutonium discovery opened a second pathway, one that promised a much faster, more direct route to an atomic bomb.

UNDER NORMAL CIRCUMSTANCES, SEABORG and his collaborators would have trumpeted their discovery from the rooftops. But the war was on, and Allied scientists didn’t want to aid the Nazis, so they filed a secret report with the government, and kept silent. 55 Unfortunately, their self-censorship came too late. A year earlier Seaborg’s colleagues and a Princeton physicist had published two articles in the American scientific journal The Physical Review suggesting that a nuclear chain reaction would produce a fissionable atom. An associate of Heisenberg read it and alerted Germany’s Weapons Research Office.

From then on nuclear fission research in Germany, Britain and the United States split along two tracks: one, developing an industrial technology to separate U235 atoms from uranium for a uranium bomb; the other, building a nuclear reactor which could generate power and produce fuel for a plutonium bomb. Enrico Fermi and Werner Heisenberg both focused on the reactor. 56

To get started, Heisenberg needed a “moderator” to slow the millions of speeding neutrons emitted by the chain reaction. Graphite seemed the best choice. Its carbon atoms, arranged in lattice-like layers, would serve as an obstacle course forcing the neutrons to slow down as they passed through. But there was a problem. When Heisenberg’s colleagues ran their experiments, impurities in the graphite absorbed many of the neutrons. Heisenberg decided to use a rare liquid chemical called “heavy water” instead.

Meanwhile, Fermi and Leo Szilard, a Hungarian Jew who had fled Europe when Hitler came to power, also tried using graphite. But Szilard, anticipating the impurity problem, went directly to his supplier, the National Carbon Company, and arranged to purchase the purest graphite they could produce. His tests showed the purified graphite would work. Graphite had two important advantages over heavy water: it was relatively inexpensive and readily available.

THE STAGE WAS SET. On a hot August morning in 1941, Fermi, Szilard and colleagues launched their first attempt to build a full-scale nuclear reactor. As Fermi supervised, a hired team of Columbia University football players began hauling eight tons of uranium-filled canisters and 30 tons of graphite blocks into the basement of Columbia’s natural sciences building where they assembled them into a large cube.

Albert Einstein had compared the harnessing of nuclear energy to the futility of “shooting in the dark at scarce birds.” It was an apt comparison. Splitting the U235 nucleus with neutrons and shooting the scarce birds were both crapshoots with extremely poor odds of success.

Uranium ore contains only one U235 nuclear energy storehouse for every 139 U238 atoms. The neutrons that Fermi used to bombard the uranium were far more likely to encounter one of those other atoms or escape through gaps between atoms as they were to unlock one of the storehouses. To succeed, Fermi had to figure out a way to stack the deck, to ramp up the chances of a neutron/U235 encounter.

After months of experimenting with different reactor designs, he and his colleagues came up with a plan: if they took uranium powder (the only form available for purchase), packed that powder to just the right density, just the right moisture content, in cans of just the right size and shape; and, if they embedded those cans in bricks of graphite of just the right purity, and they positioned them just the right distance from each other in a mass of just the right shape and volume, then possibly . . . just possibly . . . they could slow down enough neutrons and direct them to split enough U235 atoms that they could sustain a chain reaction. 57

In September of ’41, Fermi’s first attempt fell short of his goal. The successive generations of split U235 nuclei emitted large numbers of neutrons, but not enough to keep the chain reaction going.