The Hiroshima bomb was far more physically damaging to Tsutomu Yamaguchi. Although the Nagasaki bomb (Fat Man) was technically the more powerful weapon, Yamaguchi was caught outdoors and unshielded in Hiroshima, suffering severe burns, ruptured eardrums, and radiation exposure. In Nagasaki three days later, he was inside a reinforced office building at a similar distance from ground zero and escaped without new major injuries. The real danger of the second bomb was invisible: a second massive dose of radiation that compounded the first and shaped the rest of his life.
Hiroshima: Caught in the Open
On the morning of August 6, 1945, Yamaguchi was a 29-year-old engineer on a business trip for Mitsubishi Heavy Industries. He was less than two miles (roughly 3 kilometers) from ground zero when Little Boy detonated. He was outdoors with no substantial cover. The thermal flash seared the left side of his body, leaving him with serious burns across his face and arms. The blast wave ruptured his left eardrum, causing permanent hearing loss in that ear. Temporary blindness followed. He was badly enough injured that he needed to be bandaged extensively before making the journey home.
Despite his condition, Yamaguchi spent the night in Hiroshima and then traveled back to his hometown of Nagasaki, arriving on August 8. He reported to work the following morning, still wrapped in bandages, and began describing the Hiroshima explosion to his supervisor.
Nagasaki: Shielded by a Building
At 11:00 a.m. on August 9, while Yamaguchi was in his Mitsubishi office recounting what had happened in Hiroshima, the B-29 bomber Bockscar dropped Fat Man over Nagasaki. By coincidence, his workplace put him almost exactly the same distance from ground zero: about 3 kilometers, or 1.9 miles. This time, however, he was inside a solid building. The structure absorbed much of the blast wave and shielded him from the thermal pulse that had burned him so badly three days earlier.
The explosion blew off his bandages and exposed him to another surge of radiation, but he was not burned again and sustained no new blast injuries. He described himself as “relatively unhurt” by the second detonation, at least in terms of immediate physical trauma. His bandages were ruined and could not be replaced in the chaos that followed, leaving his Hiroshima burns exposed and harder to treat during the critical healing window.
Why Hiroshima Did More Immediate Damage
The difference came down to shielding, not bomb strength. Fat Man, the Nagasaki weapon, was actually the more powerful of the two. It used a plutonium implosion design and produced a larger explosive yield than Little Boy’s uranium gun-type mechanism. If Yamaguchi had been standing outdoors at the same distance in Nagasaki, his injuries could have been even worse than in Hiroshima.
But the physics of nuclear blasts make cover enormously important. The thermal radiation that causes flash burns travels in straight lines, so even a single wall between a person and the fireball can block it entirely. The blast wave weakens rapidly with distance, and a reinforced structure absorbs much of the overpressure that would otherwise crush or throw a human body. In Hiroshima, Yamaguchi had none of that protection. In Nagasaki, the office walls did the work his body had absorbed the first time.
The Invisible Damage of Nagasaki
Where the Nagasaki bombing did its real harm was through radiation. Yamaguchi’s body, already saturated with radiation from Hiroshima, absorbed a second large dose. Radiation damage is cumulative. The combined exposure from both blasts set the stage for a long list of health problems that unfolded over decades.
His son, writing years later through Nagasaki University, described the effects in detail. The Hiroshima explosion had ruptured his inner ear, leaving him permanently bent toward people when they spoke, always listening with his right side. He developed cataracts, later identified as caused by the intense light of the atomic flash. Around age 40, he experienced reproductive dysfunction. He also suffered from leukemia, a cancer of the white blood cells strongly linked to radiation exposure. Late in life, he developed an advanced cancer that spread throughout his body and was inoperable due to his age.
These long-term consequences cannot be neatly separated into “caused by Hiroshima” or “caused by Nagasaki.” Both doses contributed. But the second exposure in Nagasaki was critical because it pushed the total radiation burden well beyond what his body received in Hiroshima alone. In that sense, while the Nagasaki bomb did less visible damage in the moment, its contribution to his cumulative radiation load made his long-term health outcomes significantly worse than they would have been from a single bombing.
Official Recognition as a Double Survivor
Japan recognized atomic bomb survivors, known as hibakusha, for decades after the war, granting them access to medical benefits and government support. But Yamaguchi was not officially certified as a survivor of both bombings until 2009, when he was 93 years old. He became the first person ever granted this double certification by the Japanese government. “My double radiation exposure is now an official government record,” he told The Mainichi Daily News at the time. He died the following year, in January 2010, at age 93.