Oppenheimer: The Real WW2 History Behind the Decision to Drop the Atomic Bomb on Japan

This article contains mild Oppenheimer spoilers.

At 8:15 a.m. on the morning of Aug. 6, 1945, an American B-29 bomber called the Enola Gay arrived at its target above the heart of Hiroshima, Japan. Below was a city that had been left relatively untouched by the ravages of the brutal Second World War. That changed to horrifying effect after the B-29 dropped its payload above a bridge at the city’s center: an atomic bomb codenamed “Little Boy.” It would be the first nuclear weapon deployed in anger in the history of humanity. The second came three days later when another A-bomb was dropped on the Japanese city of Nagasaki.

Nearly 80 years later, the carnage and horror these weapons inflicted remain infamous. With each bomb, 40,000 people—men, women, and children—were vaporized in an instant by the heat of an atomic flash. Thousands more perished from the devastation inflicted by the fireball which followed. The exact number of fatalities is in fact difficult to estimate because while the deaths caused by radiation poisoning began within weeks of the bombings, citizens of Hiroshima were still dying from the lingering side effects more than half a century later. It is estimated the final death toll exceeded 220,000 people.

The impending horror of this hangs like the sword of Damocles above Christopher Nolan’s Oppenheimer, a stunning and apocalyptic biopic about the man who led the Manhattan Project, which gave the U.S. nuclear power and earned J. Robert Oppenheimer the title “Father of the Atomic Bomb.” Yet just as the film shies away from actually depicting the Japanese perspective of the bombing—the film is told entirely from the vantage point of either Oppenheimer (Cillian Murphy) or his political Salieri, U.S. Atomic Energy Commission Chairman Lewis Strauss (Robert Downey Jr.)—the picture also barely lets audiences into the decision-making process to drop nuclear weapons on Japan.

That said, one of the movie’s most chilling scenes is U.S. Secretary of War Henry Stimson (James Remar) meeting with a coterie of military officers, plus Oppenheimer, and matter-of-factly discussing the list of 12 possible Japanese cities to use the atom bomb on. He then awkwardly smiles as he takes Kyoto off the list because of its cultural significance to the Japanese people, and because “I honeymooned there.”

In the same scene Matt Damon’s General Leslie Groves explains they’re going to drop two bombs, one to show the enemy the U.S. now has the power of the gods, and a second time to show “we can keep doing it.” (In actuality, the U.S. would not be able to develop a third nuclear bomb for some months after the Nagasaki attack, although the Japanese government would not know this.)

For many viewers, this is a disturbing window into the past, but the window is in the shape of a keyhole. We only see it from Oppenheimer’s viewpoint, and how he was initially in lockstep with the military. But just as his own opinion on his creation quickly evolved after it was used in warfare, so have historians debated the actual rationalizations and choices made by President Harry Truman before he authorized the use of nuclear weapons—and ended the war in a matter of days through the blight of two mushroom clouds.

To Save Lives?

For his fairly seminal biography Truman, American historian David McCullough once said, “If you’re looking for an explanation for why the Allies made the decision to use the bomb, the word is ‘Okinawa.’” This most definitely gets to the essence of what seemed like an easy decision for most Americans in 1945, including Harry Truman.

Well before Truman took office, fighting in the Pacific had been monstrous, even by the standards of World War II. Imperial Japan’s standards of warfare in the lands they conquered, from Manchuria to Korea, was nightmarish and that did not change when Americans entered the war following the bombing of Pearl Harbor. At the Battle of Saipan in 1944, 3,500 American soldiers died while 30,000 Japanese soldiers were also killed. And they just didn’t die in battle. To surrender while defending their Emperor Hirohito (who was viewed as a living god) was considered a disgraceful dishonor. So more than 4,000 Japanese, including soldiers and civilians, attacked in the biggest banzai charge in history with bayonets, swords, and bamboo spears. They died almost to a man, and many of those who weren’t killed in the initial charge then died in a mass suicide by jumping off cliffs in order to avoid capture. This, too, included civilians.

Okinawa, the last major island to be taken before an invasion of mainland Japan, however, was something else. The battle began on April 1, 1945; Truman did not even become president until the death of Franklin D. Roosevelt on April 12. Fought over about three months, Okinawa saw 12,000 Americans die and another 60,000 be wounded; meanwhile 92,000 Japanese soldiers fought and died, again almost to a man, while another 150,000 civilians also perished. For perspective, within the first three months of Truman’s presidency, the U.S. casualty rate in the Pacific doubled.

In the aftermath, there was still the invasion of mainland Japan to come. Slated to begin on Nov. 1, 1945, the calculations for the death toll from what was essentially a Japanese D-Day was debated. But by any metric, it would be severe. When we mentioned some modern (and lower) estimates to actor Matt Damon of around 100,000 dead Americans, he told us during an interview conducted before the SAG-AFTRA strike, “Or more. Or more. The estimates, I think, were 250,000 to a million in a land invasion of Japan. So these are impossible questions and unanswerable questions. Unimaginable decisions.”

Indeed, when facing what could turn into protracted guerrilla warfare with both millions of Japanese soldiers and a civilian population that was being trained with bamboo spears—including women and children—to fight and die for their emperor, the U.S. Army estimated they would see 863,000 casualties with fighting going into 1947 (this did not include Navy, Marine, or obviously Japanese deaths). Meanwhile, former President Herbert Hoover oversaw a commission that predicted 500,000 American deaths and around seven million dead Japanese if a land invasion should occur. American POWs in Japan were informed by their captors that they would all be immediately executed if Americans set foot on the homeland.

So the official logic was to save at least several hundred thousand American lives (and collectively a larger number of Japanese civilians) by committing what could be considered a war crime—and arguably comparable to the firebombing atrocities Americans had already committed on Tokyo that left 100,000 civilians dead.

However, there is a historical debate about whether there were other alternatives considered and dismissed out of hand. And those are the alternatives that ultimately came to haunt J. Robert Oppenheimer….

The Counterargument

After the fall of Nazi Germany, heads of the Allied Powers had their last diplomatic meeting in late July 1945 at the ruined German city of Potsdam, which was now under Soviet control. As hinted in the movie Oppenheimer, Truman chose to obliquely speak about the atomic bomb in only abstract terms to Soviet Premier Joseph Stalin, obfuscating the biblical terror of such a weapon. At the end of the meeting, Truman had the Allies issue an ultimatum to Japan: Surrender unconditionally or expect “the utter devastation of the Japanese homeland.”

This insistence on unconditional surrender, and the failure to genuinely warn Japan about just what kind of nuclear mayhem awaited if they did not, has come under intense scrutiny from some historians, particularly given the argument that the Japanese government might have surrendered without the much dreaded land invasion.

As far as the actual Oppenheimer was concerned in the days leading up to the bomb’s dropping, this was a decision made in seeming good faith by the military. Out of naïveté or pure pragmatism, Oppenheimer did not think he could publicly pressure the Pentagon, as many other Manhattan Project scientists did by signing a petition to not use the nuclear bomb on Japan after Germany was defeated. But he did unsuccessfully attempt to sway military thinking behind the scenes.

Oppenheimer never spoke out against using the bomb on Japan, but in 1945 he was determined to persuade the Truman administration to warn the Soviets ahead of its deployment in the hopes of staving off a nuclear arms race. In Oppenheimer’s ideal future, nuclear weapons would be banned in the burgeoning United Nations and the superpowers could jointly verify that each of their governments (and all others beneath their spheres of influence) were not developing new atom bombs.

The beginning of his failed influence occurred in several meetings with Secretary of War Henry Stimson and other military personnel (which is condensed to one scene in Nolan’s movie). During the actual first meeting, Stimson ended the discussion by saying that they would not target a civilian area, per se, but they should seek a target that would leave a “profound psychological impression” on the Japanese. He also agreed with Harvard President James Bryant Conant that they should aim to hit many workers and workers’ houses (and therefore workers’ families, including children). As Kai Bird and Martin J. Sherwin wrote in their biography, American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer, “Thus, with such delicate euphemisms, did the President of Harvard University select civilians as the target of the world’s first atomic bomb.”

While these discussions were going on, a growing counterpoint was emerging within the government that suggested a nuclear demonstration to the Japanese on a barren island could be implemented, and which might have the same effect of scaring Japan into submission. This was the conclusion of the Franck Report, which was signed by several prominent nuclear physicists in June 1945. It never reached Truman’s desk though; the Army seized the report and immediately classified it. Meanwhile, Manhattan Project scientist Robert Wilson suggested to Oppenheimer they invite Japanese delegates to the Trinity test in July 1945 so they could see firsthand the horror of the bomb. When asked what if the bomb didn’t go off, Wilson bleakly said, “Well, we could kill them all.”

But what some historians offer as a counterfactual history is that the Truman administration had evidence Japan might surrender without ever even knowing about the atomic bomb. This is based largely on the Americans intercepting a Japanese cable to Russia that summer. Before Russia agreed to declare war on Japan at Potsdam, which was expected to occur by Aug. 15, the Japanese were hopeful that they could negotiate friendlier terms from the Russians than they could with the Americans. Already the U.S. was demanding unconditional surrender, which would include giving up every inch of imperial territory, submitting to American occupation, and eventually enduring a democratic election. The fear was this would lead to the Japanese emperor being deposed or even tried for war crimes like Nazi leaders were already experiencing in Germany.

Some Americans came to the conclusion that if “unconditional” was dropped from the terms of surrender, and the emperor was guaranteed a symbolic title, a surrender could be attained before the November invasion of Japan without dropping nuclear bombs. William D. Leahy, a naval admiral and chief of staff to the commander in chief (essentially first chairman of the Joint Chiefs), wrote in his diary on June 18, “It is my opinion at the present time that a surrender of Japan can be arranged with terms that can be accepted by Japan.” General Dwight D. Eisenhower also wrote he told Stimson he thought they could get Japan to surrender before November without unleashing “that awful thing.” Finally, after meeting with Stalin on July 18 in Potsdam, Truman put in his diary that the Soviets would be in the war by Aug. 15. “Fini Japs when that comes about,” Truman wrote.

Among others who sought to convince Truman to pursue diplomatic pressure on Japan and warn them about the nuclear bomb before using it was John McCloy, the assistant Secretary of War. In fact, the only cabinet member who remained purely hawkish was Secretary of State James F. Byrnes, who along with Truman saw it as politically expedient that Japan unconditionally surrender, as opposed to having a negotiated peace. Byrnes also later said, “It was ever present in my mind that it was important that we should have an end to the war before the Russians came in.”

So the counterargument goes Truman had every reason to believe the Japanese could be persuaded to surrender without using the nuclear bombs after Russia entered the war in August, and the key reason they did not allow that to happen was to announce nuclear power to the world, including the Soviets, and to keep the USSR from carving up Southeast Asia like they were already doing in eastern Europe and Germany.

It should be noted, such thoughts eventually seemed to color Oppenheimer’s mind. When the bomb was initially tested at Trinity, Oppie told The New York Times, “Lots of boys not grown up yet will owe their lives to it.” But in the weeks leading up to the Hiroshima bombing, he began succumbing to regret and self-doubt. He was spotted walking alone in the mornings around Los Alamos, puffing his pipe and repeatedly muttering, “Those poor little people.” After the war, Oppenheimer came to the conclusion he was misled about the necessity of bombing Japan and grew heavily skeptical of government officials.

This view of history is a disturbing one, suggesting that out of revenge against an admittedly cruel enemy, or realpolitik cynicism, not every alternative was pursued or exhausted before a terrifying weapon obliterated hundreds of thousands of civilians. As even Stimson told Oppenheimer, the atomic bomb was not a “new weapon, merely, but a revolutionary change in the relation between man and the universe. It could become a Frankenstein which eats us up, or it could secure the global peace.” 

With that said, I cannot assess any of this in good conscience without mentioning my own grandfather, David O. Crow. He was an American G.I. who was at Pearl Harbor when it was bombed; he also saw the banzai charge and much else on Saipan; and he was in the hell of Okinawa. He never spoke much about any of it, but when I once asked how he felt about the dropping of the nuclear bombs, he said in his typically laconic manner that he and his friends were relieved. “We had had enough.”

While there was internal debate in the Truman administration about whether the Soviets entering the Pacific would cause the Japanese to surrender, Oppenheimer’s belief that one nuclear bomb would terrify the imperial government to defeat did not come to pass. After the horrors of Hiroshima, Japan did not surrender. Nor did they surrender a day later when the Russians declared war on Aug. 7. And even after Nagasaki, half of Japan’s Supreme Council for the Direction of the War refused to surrender. They urged their emperor to fight on, even under the false belief the Americans had more nuclear bombs ready for more cities. It was the emperor, only after two nuclear bombs, who finally overrode his generals and submitted to an unconditional surrender (but one which still kept him in a ceremonial position).

Consider that in that same summer when American officials debated the likelihood of surrender, a Japanese naval officer told his emperor Japan would not surrender even if it meant “sacrificing 20 million Japanese lives.” After the nuclear bombs fell, those same voices still resisted surrender, Emperor Hirohito had simply seen enough to finally ignore them. The chief cabinet secretary later said, “The atomic bomb was a golden opportunity given by heaven for Japan to end the war.”

It is easy to say with certainty three-quarters of a century later that Japan would have capitulated with less pressure, but the realities of that horrible summer seem less absolute, and less clear, even after the first mushroom cloud. As Damon said, these are impossible questions.

Oppenheimer is in theaters now.