In the final months of World War II, as Nazi Germany began to crumble, capturing Berlin had become the ultimate political and military prize. For the Allies—Britain, the United States and the Soviet Union—this was the chance to take the symbolic seat of Hitler’s expansionist, and genocidal, regime.

But there was another objective. Though much of Germany’s advanced research and development around atomic weaponry had by this point been evacuated to points outside the city, many of the nation’s greatest scientific minds remained in or around the capital. Harnessing their expertise might be the key to future world dominance—something both the Americans and the Soviets were keen to seize.

Who would be the victor, and at what cost? As the war wound down in early 1945, British and American forces began to close in on Berlin from the West, while Russia approached from the East. The Allies' uneasy partnership was growing increasingly strained: This was not just a race for the city, so much as for the upper hand in the coming postwar world order. Two mighty nations were on the cusp of becoming opposing superpowers—whose ability to “drop the big one” drove the stakes for humanity ever higher.

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A year before, in early 1944, U.S. General Dwight D. Eisenhower, supreme commander of the Allied Expeditionary Force, had been all in on the idea of capturing the German capital: “Berlin is the main prize,” he wrote to his British counterpart, Field Marshal Bernard Montgomery. “There is no doubt whatsoever, in my mind, that we should concentrate all our energies and resources on a rapid thrust to Berlin.” But by the end of 1944, rapid Soviet advancement began to throw this objective into question. By early 1945, the Red Army was barely 40 miles out of Berlin. British-American forces, set back by the Battle of the Bulge in Ardennes, had yet to cross the Rhine.

In late March, even as British and American forces got closer, Eisenhower telegrammed Soviet Premiere Joseph Stalin to say Berlin was no longer the objective, and that the Americans would stand pat at the Elbe River. Stalin seemed to agree—but ordered a massive Soviet offensive to capture the city by April 16, just three days later.

But by contacting Stalin directly, without first consulting the other two “Big Three” Allied political leaders, British Prime Minister Winston Churchill and U.S. President Franklin Delano Roosevelt, Eisenhower had angered the British leader. In a series of telegrams at the end of March, Churchill fervently objected to Eisenhower’s decision—and urged him to press on.

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They had good reasons to keep the Soviet army from reaching Berlin first. Given Stalin’s interest in extending his Communist sphere of influence in Europe, it was likely his armies would secure Vienna, and from there, all of Austria. Churchill also worried about political ramifications—in particular, how Russia would perceive its role in the war effort if it captured Berlin, and what that could mean for their future dealings. And to top it off, he was irritated that the British Army had been relegated “to an unexpectedly restricted sphere.”

Churchill reiterated this point to Roosevelt, writing: “If [the Soviets] also take Berlin, will not the impression that they have been the overwhelming contributor to our common victory be unduly imprinted on their minds?”

Roosevelt died of a cerebral hemorrhage less than two weeks later. And Eisenhower, who had been keeping his options open, even after the telegram to Stalin, ultimately decided that beating Russia to the finish line was simply too costly. General Omar Bradley had warned that it might cost the U.S. military upward of 100,000 American lives to make its way to Berlin—a price Eisenhower wasn’t willing to pay for territory he would ultimately have to cede to the Soviets, per the terms of postwar occupation already drawn up by the Big Three at the Yalta Conference months earlier. Berlin was looking to him like more a prestige get than a strategic one.

Years later, speaking to the British journalist Alistair Clarke in the late 1960s, Eisenhower justified his decision—one many historians considered the most controversial of his career. With Germany already divided into two occupation zones, “there was no possibility of the Western Allies capturing Berlin and staying there,” he said. The U.S. army would have had to retreat 125 miles back into its own zone as quickly as the fighting was over. “When my final plans were issued, we were about 200 miles to the westward of Berlin. The Russians, ready to attack, were 30 miles off Berlin, eastward, but with a bridgehead already west of the Oder River,” he said. “It didn’t seem like good sense to try, both of us, to throw in forces toward Berlin and get mixed up—two armies that couldn’t talk the same language, couldn’t even communicate with each other. It would have been a terrible mess.”

Allowing the Russians first passage into Berlin, however, had other costs. Since September 1943, America’s top-secret Alsos Mission had been working avidly to uncover the German nuclear energy project and find its facilities and brain trust. Scientists in that country had discovered nuclear fission in 1938 and had been stockpiling uranium and other nuclear raw materials in anticipation of an A-bomb breakthrough. U.S. forces had already taken key Italian scientists into custody after the fall of Rome. After rolling into Berlin, the Russians would be in prime position to do the same in Germany.

Adolf Hitler had fortified Berlin to the very best of his ability, declaring it a Festung, or fortress, in February 1945. German defenses proved so tenacious, in fact, that Russian troops would take nine days to break into the city, on April 24. On April 30, Hitler, hiding in his private bunker deep beneath the Reich chancellery, committed suicide. the Germans defending Berlin surrendered to the Soviets—though fights between German units and the Red Army continued to smolder in the city’s suburbs.

A few days before Berlin was officially captured, a leading Soviet general, who was also a chemist, arrived in an armored vehicle at the castle of Baron Manfred von Ardenne, a prominent applied physicist and inventor who had designed Hitler’s radio system. He handed von Ardenne a protective letter, or “schutzbrief”—an overture to a formal request, days later, to continue his research on isotope separation in the USSR. Von Ardenne, as well as many of his peers, jumped at the opportunity.

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Others, such as the top scientist Wernher von Braun, who was in hiding in Austria, opted to surrender to U.S. forces. “We knew that we had created a new means of warfare, and the question as to what nation, what victorious nation we were willing to entrust this brainchild of ours was a moral decision more than anything else,” he told the press. “We felt that only by surrendering such a weapon to people who are guided by the Bible could such an assurance to the world be best secured.”

In the months that followed, thousands of German scientists, engineers and technicians would be rounded up and recruited by these two sides. Through America’s Operation Paperclip, more than 1,600 German scientific minds were resettled to the U.S. between 1945 and 1959. The USSR, meanwhile, had a plan of its own: Operation Osoaviakhim, as it was called, resulted in the deportation and forcible recruitment of more than 2,200 German specialists in a single night in October 1946.

In both the U.S. and the USSR, these thinkers would be put to work developing terrifying weapons of the sort the world had never seen—ushering in the half-century Cold War.

Watch full episodes of World War II: Race to Victory.