American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer

President Harry Truman’s use of atomic weapons against the Japanese cities of Hiroshima and Nagasaki remains one of the most controversial decisions in the history of warfare. As with all historical events, Truman’s decision can be properly evaluated only in light of circumstances that existed in 1945. With these circumstances in mind, good evidence exists on both sides of the controversy.

Truman’s defenders have argued, foremost, that the atomic bomb ultimately saved US and Japanese lives because, without it, the US would have launched a costly invasion of the Japanese home islands. In this scenario, the Japanese would have defended their islands to the end. Throughout the Pacific War, the Japanese had fought with relentless and even “suicidal” ferocity given the kamikaze air attacks (beginning in October 1944), in which Japanese pilots resorted to intentionally crashing their planes into US warships. In the spring and summer of 1945, the Battle of Okinawa resulted in high casualties on all sides, including Okinawan civilians. Therefore, a reasonable assumption was that an invasion of Japan, which might have occurred as early as November 1, 1945, would have cost many thousands of lives.

On the other hand, Truman’s critics have contended that no such invasion would have occurred. According to this view, by August 1945 the Japanese were close to quitting and in fact were looking for a way to end the war that did not require unconditional surrender. Furthermore, Soviet dictator Joseph Stalin already had pledged to enter the war against Japan. This factor looms large in the minds of Truman’s critics because it suggests that the combined US and Soviet forces would have compelled the Japanese to surrender in short order and thereby would have rendered the expected invasion unnecessary. This view suggests that US policymakers focused on possible Soviet intervention and the postwar global order when they touted the bomb as offering a quick end to the war—although critics pointed out that the war likely would have ended soon no matter what. If so, harsh judgment of US officials in general and of Truman in particular—for murdering tens of thousands of Japanese civilians in the name of emerging Cold War diplomacy—is understandable.

A balanced view requires considering each of these perspectives along with the alternatives available to Truman in 1945. For instance, some scientists at Los Alamos argued for a demonstration of the weapon rather than its lethal deployment without warning. Policymakers opted against a demonstration, however, because by that time they had only two bombs available. Another argument is that the August 9 Nagasaki attack followed too quickly after the August 6 Hiroshima bombing.

Perhaps the most often-overlooked aspect of the atomic bomb debate involves a military option that requires no speculation; we know that US officials would have pursued this option because they had been using it for much of 1945: Had Truman decided against deploying the atomic bomb, and had the war continued, US aircraft would have firebombed Japanese cities, likely resulting in even more casualties than the atomic bombs produced. As an example, the overnight firebombing of Tokyo on March 9-10, 1945, cost more Japanese lives than either of the atomic attacks. Given that the war in Europe was over, that thousands of B-29 bombers were on their way to the Pacific, and that the US had control of airfields on nearby Okinawa, US pilots would have conducted relentless bombing runs over Japanese cities. In this scenario, the crucial phrase is “had the war continued.” If Truman’s harshest critics are correct—if the Japanese would have surrendered soon no matter what—then no such bombing would have occurred.

The controversy surrounding the decision to drop atomic bombs on Japan will likely persist, as the decision raises many ethical considerations without clear answers, which is reflected in Oppenheimer’s conflicted feelings about his legacy in the wake of the development of the weapon.