WHEN he had stopped crying, Tsutomu Yamaguchi would tell you why he called his book of poems “The Human Raft”. It had to do with the day he forgot to take his personal name-stamp to work, and had to get off the bus. Much was on his mind that morning. He had to pack his bags to leave Hiroshima after a three-month assignment as an engineer in the Mitsubishi shipyard; there were goodbyes to say at the office, then a 200-mile train journey back to Nagasaki to his wife Hisako and Katsutoshi, his baby son. He was slightly stressed when he got to his stop, still with half-an-hour’s walk ahead of him on a track that led through featureless potato fields. But it was a beautiful August day; the sky was clear, his spirits high. And then—readers will feel a tremor, but he felt none—he noticed an aircraft circling, and two parachutes dropping down.

The next thing he knew was a blaze of white magnesium light, and a huge ball of fire. He dived to the ground. The fireball, roaring upwards, sucked him up again and threw him, blinded, face-down into the mud of the potato field. He was two miles from the epicentre of the blast, in a rain of flaming scraps of paper and clothes. His upper body and half his face were badly burned, his hair gone and his eardrums ruptured. In this state, he made his way back to the devastated city to try to do what he had meant to do that day: catch the train. The river bridges were down. But one river was full of carbonised naked bodies of men, women, children, floating face-down “like blocks of wood”, and on these—part treading, part paddling—he got to the other side. His human raft.

At this point in his story he would weep uncontrollably. It was by no means the end of it. When he reached Nagasaki, barely pausing to get his burns dressed, he reported for work. His boss was sceptical: how could a single bomb have destroyed Hiroshima? Then the same white magnesium light blazed in the window, and Mr Yamaguchi was tossed to the ground again. A reinforced-steel stairwell saved him. His bandages were blown off, and he spent the next weeks curled round his raw wounds in a shelter, close to death. His house was destroyed, his wife and son saved for no reason he could see. But when schoolchildren later asked him, in awed respect, “What was the most terrible thing?”, his answer was not the dangling tongues and eyeballs, not the skin that hung off the bodies of the living “like giant gloves”—but the bridge of bodies on which he had crossed the river.

He talked about all this to Charles Pellegrino, an American writer, and Richard Lloyd Parry of the London Times. He told them that he hated the atom bomb because of “what it does to the dignity of human beings”. Walking into Hiroshima, he noticed that the bewildered crowds on the streets were mostly naked, limping children. They made no sound; indeed, no one made a sound. They were reduced—like him, as he was flung into the furrows of the potato field—to the level of mute sticks or leaves, tossed in the wind and burned, or used as floats.

Some argued that he was lucky. A deaf left ear and weak legs were the only after-effects until, late on, stomach cancer appeared. He worked as a translator, then a teacher, and eventually returned to Mitsubishi. But, as he wrote in 1969, he was not so sanguine inside.

His emotions mostly emerged in these tanka, or 31-syllable poems. He wrote hundreds, each one an ordeal. When he composed them, he would dream of the dead lying on the ground. One by one, they would get up and walk past him.

He published these poems himself in 2002, and they might have been his only testimony. But in 2005 his son Katsutoshi died of cancer at 59, killed by the radiation he had received as a baby. Mr Yamaguchi began to feel that fate had spared him to speak out against the horrors of nuclear weapons: in schools, in a documentary, in a letter to Barack Obama and even, at 90, on his first trip abroad, in front of a committee of the United Nations in New York.

At his insistence, his status was recognised by the Japanese government: he became officially (though there had been more than 100 others) the only nijyuu hibakusha, or twice-victim of the atom bomb.

He began to be comforted by three things. One was a set of drawings of the 88 Buddhas of the Shikoku pilgrimage, whose outlines—robes, haloes, calm hands—he devoutly painted in. The carbonised, face-down Buddhas of his tanka found peace again. The second comfort was in “simple acts of kindness”. And the third was an image of his life as a baton, passed on every time anyone heard or read his testimony. All these batons might form, together, another human raft.