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On August 6, 1945, the United States bomber Enola Gay cruised over the Japanese city of Hiroshima and dropped an atomic bomb, marking the first time a nuclear weapon had ever been used in warfare. Just three days later, another nuclear bomb was dropped on Nagasaki, marking the last time nuclear weapons were used in warfare.
The two cities were almost instantaneously turned to wreckage and rubble in a flash of searing light and unimaginable force, while 110,000 to 210,000 people died in the initial blasts and the ensuing effects of ionizing radiation. Two weeks later Japan surrendered, ending World War II.
Seventy-five years on, those few days of monumental destruction serve as a cautionary tale about the potential of nuclear energy and the importance of ensuring its power is never wielded in anger again. It’s also a stark reminder of how scientific progress can also bring new horrors into the world.
"It left an impression on me unlike anything else in my life, and the horror is still scorched in my mind to the extent that even now, fifty years later, I can still envision the events of that time with startling clarity," Sachiko Yasui, who survived the Nagasaki atomic bomb when she was 6 years old, wrote in an account of her experience in 1995.
"It was the saddest, cruelest, most despicable thing I have ever lived through, or ever will. It is something that I cannot forget, no matter how hard I try," recounted another survivor, Chitoshi Honda, who was 14 years old at the time of the bombing.
The origins of this event can be neatly traced back to 1938 when two German chemists, Otto Hahn and Fritz Strassmann, discovered nuclear fission. The breakthrough led to Albert Einstein writing a letter to President Franklin D Roosevelt in 1939 warning of the possibility that Germany could develop an atomic bomb. The race was on. Although no single decision created the American atomic bomb project, in 1942 a huge collaboration between the military and physicists began to look at atomic energy and, eventually, its weaponization. It became known as the “Manhattan Project”.
After three years of tireless research, the Manhattan Project succeeded in detonating the first nuclear bomb in the Jornada del Muerto desert, New Mexico on July 16, 1945.
“We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent,” Robert Oppenheimer, the "father of the atomic bomb," who played a chief role in designing the first nuclear weapons, said in an infamous 1965 television interview.
“I remembered the line from the Hindu scripture, the Bhagavad Gita; Vishnu is trying to persuade the Prince that he should do his duty and, to impress him, takes on his multi-armed form and says, ’Now I am become Death, the destroyer of worlds.’"
A nuclear bomb yields its destructive power from nuclear reactions. In the case of the early atomic bombs, such as those used in Hiroshima and Nagasaki, this is a fission reaction. Fission occurs when a neutron strikes the nucleus of an isotope, such as uranium-235 and plutonium-239, splitting the nucleus and releasing a huge amount of energy and neutrons. The newly released neutrons then strike other nuclei, splitting them to release more energy and more neutrons, and so on. This chain reaction almost instantaneously releases a tremendous amount of energy, notably more than any conventional explosive.
Within a month of being first tested, this god-like force was being dropped on humans. Nazi Germany surrendered to Allied forces in May 1945, but World War Two continued to rage in the Pacific Theatre between the Allies and Imperial Japan. After Tokyo rejected an ultimatum for peace, the US argued the use of nuclear weapons would force a quick surrender and win the war. Many historians, however, have since doubted that the use of atomic bombs was necessary to end the war.
At 8.15 am on August 6, 1945, the Enola Gay aircraft dropped a 16-kilotonne nuclear bomb on Hiroshima. The bomb, codenamed "Little Boy,” was loaded with 64 kilograms (141 pounds) of highly enriched uranium-235. The blast radius was about 1.6 kilometers (1 mile), with radiation spreading about 4.8 kilometers (3 miles). Estimations of between 70,000 and 140,000 people, mostly civilians, died that day. The city of Nagasaki met a similarly grim fate in the early morning of August 9, 1945, with the deployment of "Fat Man," a nuclear bomb armed with a solid plutonium core.
“Large numbers of people had flocked to the tunnel factory to avoid an air raid… Suddenly the electricity in the tunnel went out, leaving us in darkness,” Yasumi Yoshitomi, a survivor of the Nagasaki atomic bombing, described in a lecture about their experience.
“At exactly the same time, a burst of light so bright that it seemed to pierce our eyes flashed at the tunnel entrance, 100 meters away. Then a tremendous blast wind came blowing in like a great typhoon. The people at the front of the tunnel shrieked as they were thrown through the air and against the machinery or the dirt floor, where they lay unmoving.”
In Hiroshima, the fireball created by the bomb destroyed 13 square kilometers (5 square miles) of the city. The intensity of the blast heated the ruins to such a degree, it resulted in a firestorm that ravaged the city for hours. The level of destruction and death was unfathomable.
“There was so much smoke in the air that you could barely see 100 meters ahead, but what I did see convinced me that I had entered a living hell on earth,” Sunao Tsuboi, a survivor of the Hiroshima bombing, told The Guardian in 2015. “There were charred bodies everywhere, including in the river. I looked down and saw a man clutching a hole in his stomach, trying to stop his organs from spilling out. The smell of burning flesh was overpowering.”
But the legacy of the atom bombs was much longer than this hellish summer. One of the consequences of nuclear weapons is the longstanding effect they have on people, animals, and the surrounding environment long after the event. Numerous studies have noted that a significant number of survivors have an increased incidence of cancer as a result of the bombs’ lingering radiation. Although the precise extent has been disputed, one estimate suggests that at least 62,000 in Hiroshima alone have died as a result of the atom bomb since 1946.
Even after the atomic bombing of Hiroshima and Nagasaki, Japan did not instantly surrender and some US leaders were hungry to drop another atomic bomb. Fortunately, Japan announced its unconditional surrender on August 15, 1945. The 40-odd years that followed continued to keep nuclear tensions sky-high, although nuclear weapons have not been used in warfare since these two attacks.
The high stakes game is still continuing today. At least 13,865 warheads were in existence at the start of 2019, owned by nine nations: the US, Russia, the UK, France, China, India, Pakistan, Israel, and North Korea. With international tensions between nuclear states continuing to bubble, the world can only hope that the lessons of August 1945 are never forgotten.
"On this tragic anniversary, we ask political and military leaders around the world to join us—to demonstrate that nuclear weapons do not create safety or security, but diminish them and threaten humanity’s future," the Bulletin of the Atomic Scientists said in a statement.
"With the fantasy that they are useful dispelled, nuclear weapons may come to be viewed for what they are—a costly and dangerous detour from the path toward real global security."
