We are on our way to bomb the mainland of Japan. Our flying contingent consists of three specially designed B-29 Superforts, and two of these carry no bombs. But our lead plane is on its way with another atomic bomb, the second in three days, concentrating its active substance, and explosive energy equivalent to 20,000, and under favorable conditions, 40,000 tons of TNT.

We have several chosen targets. One of these is the great industrial and shipping center of Nagasaki, on the western shore of Kyushu, one of the main islands of the Japanese homeland.

I watched the assembly of this man-made meteor during the past two days, and was among the small group of scientists and Army and Navy representatives privileged to be present at the ritual of its loading in the Superfort last night, against a background of threatening black skies torn open at intervals by great lightning flashes.

It is a thing of beauty to behold, this "gadget." In its design went millions of man-hours of what is without a doubt the most concentrated intellectual effort in history. Never before had so much brain-power been focused on a single problem.

This atomic bomb is different from the bomb used three days ago with such devastating results on Hiroshima.

I saw the atomic substance before it was placed inside the bomb. By itself it is not at all dangerous to handle. It is only under certain conditions, produced in the bomb assembly, that it can be made to yield up its energy, and even then it gives up only a small fraction of its total contents, a fraction, however, large enough to produce the greatest explosion on earth.

The briefing at midnight revealed the extreme care and the tremendous amount of preparation that had been made to take care of every detail of the mission, in order to make certain that the atomic bomb fully served the purpose for which it was intended. Each target in turn was shown in detailed maps and in aerial photographs. Every detail of the course was rehearsed, navigation, altitude, weather, where to land in emergencies. It came out that the Navy had submarines and rescue craft, known as "Dumbos" and "Super Dumbos," stationed at various strategic points in the vicinity of the targets, ready to rescue the fliers in case they were forced to bail out.

The briefing period ended with a moving prayer by the Chaplain. We then proceeded to the mess hall for the traditional early morning breakfast before departure on a bombing mission.

A convoy of trucks took us to the supply building for the special equipment carried on combat missions. This included the "Mae West," a parachute, a life boat, an oxygen mask, a flak suit and a survival vest. We still had a few hours before take-off time but we all went to the flying field and stood around in little groups or sat in jeeps talking rather casually about our mission to the Empire, as the Japanese home islands are known hereabouts.

In command of our mission is Major Charles W. Sweeney, 25, of 124 Hamilton Avenue, North Quincy, Massachusetts. His flagship, carrying the atomic bomb, is named "The Great Artiste," but the name does not appear on the body of the great silver ship, with its unusually long, four-bladed, orange-tipped propellers. Instead it carried the number "77," and someone remarks that it is "Red" Grange's winning number on the Gridiron.

Major Sweeney's co-pilot is First Lieutenant Charles D. Albury, 24, of 252 Northwest Fourth Street, Miami, Florida. The bombardier upon whose shoulders rests the responsibility of depositing the atomic bomb square on its target, is Captain Kermit K. Beahan, of 1004 Telephone Road, Houston, Texas, who is celebrating his twenty-seventh birthday today.

Captain Beahan has been awarded the Distinguished Flying Cross, the Air Medal, and one Silver Oak Leaf Cluster, the Purple Heart, the Western Hemisphere Ribbon, the European Theater ribbon and two battle stars. He participated in the first heavy bombardment mission against Germany from England on August 17, 1942, and was on the plane that transported General Eisenhower from Gibraltar to Oran at the beginning of the North African invasion. He has had a number of hair-raising escapes in combat.

At 08.00 a warning light on the black box in Sweeney's aircraft indicated a fault in the bomb. It was far too late to start testing all the circuits, and Ashworth made an intuitive guess; he found and repaired the faulty switches. But Sweeney now had an additional worry. He had done two runs onto Kokura from opposite points of the compass without managing a visual, and when his flight engineer reported the fuel level as dangerously low, he left for Nagasaki, telling his bomb-aimer, Captain Beahan, that they could only afford one run and if there was no visual sighting it would have to be a no drop. The weather on the approach run was even worse than Kokura, and it began to dawn on Sweeney that with no fuel latitude he would have to fly a direct course to Okinawa, the nearest emergency landing field, and jettison the bomb over the first open stretch of sea that was clear of shipping. At 10.00, with the city still visible only on radar, Beahan suddenly shouted: "I've got it. I see the city. I'll take it now." One minute later, at 11.01, the bomb dropped, Sweeney went into a rate-four turn to get as far away as possible from the shock waves, and Bock, flying behind him, dropped the instrument capsule in which was Alvarez' record message to Sagani.

For the past twenty minutes we had been staring intently around us looking for the explosion and wondering what on earth could have happened to Sweeney. All we saw was smoke coming from a town, the result of a medium bomber raid, until there was a cry on the intercom and to port we saw a gigantic plume of billowing white smoke. "Yes, that's it," I shouted, but I was wrong; it was an incendiary attack on a town of mostly wooden houses. Quite what warned us I am not certain - I think perhaps a fleeting flash - but we all seemed to know as if by instinct, for there was a simultaneous cry and Hopkins swung the nose round to starboard and into line with the flash of light. The ultra-dark glasses we each had round our foreheads to protect our eyes from the blinding light of the bomb were not needed because we were about fifty miles away. By the time I saw it, the flash had turned into a vast fire-ball which slowly became dense smoke, 2,000 feet above the ground, half a mile in diameter and rocketing upwards at the rate of something like 20,000 feet a minute. I was overcome, not by its size, nor by its speed of ascent but by what appeared to me its perfect and faultless symmetry. In this it was unique, above every explosion that I had ever heard of or seen, the more frightening because it gave the impression of having its immense power under full and deadly control. "Against me", it seemed to declare, "you cannot fight." My whole being felt overwhelmed, first by a tidal wave of relief and hope - it's all over! - then by a revolt against using such a weapon. But, I remembered, I had been sent here for a purpose and as best I could I must get on with my job. The cloud lifted itself to 60,000 feet where it remained stationary, a good two miles in diameter, sulphurous and boiling. Beneath it, stretching right down to the ground was a revolving column of yellow smoke, fanning out at the bottom to a dark pyramid, wider at its base than was the cloud at its climax. The darkness of the pyramid was due to dirt and dust which one could see being sucked up by the heat. All around it, extending perhaps another mile, were springing up a mass of separate fires. I wondered what could have caused them all....

We were a silent crew on our way home. I thanked Hopkins for the courtesy of a cockpit seat, and wriggled my way down the tunnel to join Bill in the central compartment. He startled me by suddenly saying: "That's only the detonator compared with the bomb that is to come." He meant the hydrogen bomb, but I asked no questions, because it was beyond my comprehension. Foremost in my mind was a growing conviction that Sweeney had missed the aiming point by two miles or more. I wondered how this could have happened with a crew that had been consistently averaging a 200-yard error from 30,000 feet, but I did not yet know the pressures under which Sweeney had been operating. He had left the target immediately after dropping the bomb and crossed the Okinawa coast with one engine dead through lack of fuel. His mayday call for an emergency landing was refused - as happened to me in precisely the same predicament over Linton-on-Ouse in 1941 coming back from Berlin - so he fired all his distress flares and kept coming in on his approach. At dispersal point they found less than 10 gallons in his wing tanks, apart from the 600 he could not use in the bomb bay. It was 12.30. His co-pilot, Lieutenant Charles Albury, went to the chapel and prayed that what they had just done would put an end to the killing.

We watched a giant pillar of purple fire, 10,000 feet high, shoot up like a meteor coming from the earth instead of outer space. It was no longer smoke, or dust, or even a cloud of fire. It was a living thing, a new species of being, born before our incredulous eyes. Even as we watched, a ground mushroom came shooting out of the top to 45,000 feet, a mushroom top that was even more alive than the pillar, seething and boiling in a white fury of creamy foam, a thousand geysers rolled into one. It kept struggling in elemental fury, like a creature in the act of breaking the bonds that held it down. When we last saw it, it had changed into a flower-like form, its giant petals curving downwards, creamy-white outside, rose-coloured inside. The boiling pillar had become a giant mountain of jumbled rainbows. Much living substance had gone into those rainbows.

I was doing some clerical work for the Japanese imperial army. At about 11 o'clock, I thought I heard the throbs of a B-29 circling over the two-storey army headquarters building. I wondered why an American bomber was flying around above us when we had been given the all-clear. There was no noise of anti-aircraft fire. We were working in our shirt sleeves; and all the windows and doors were wide open because it was so stiflingly hot and humid in our two-storey building.

At that moment, a horrible flash, thousands of times as powerful as lightning, hit me. I felt that it almost rooted out my eyes. Thinking that a huge bomb had exploded above our building, I jumped up from my seat and was hit by a tremendous wind, which smashed down windows, doors, ceilings and walls, and shook the whole building. I remember trying to run for the stairs before being knocked to the floor and losing consciousness. It was a hot blast, carrying splinters of glass and concrete debris. But it did not have that burning heat of the hypocentre, where everyone and everything was melted in an instant by the heat flash. I learned later that the heat decreased with distance. I was 2,800m away from the hypocentre.

When I came to, it was evening. I was lying in the front yard of the headquarters - I still do not know how I got there - covered with countless splinters of glass, wood and concrete, and losing blood from both arms. I felt dull pains all over my body. My white short-sleeved blouse and mompe (the authorities ordered women, young and old, to wear these Japanese-style loose trousers) were torn and bloody. I felt strangely calm. I looked down at my wrist watch; it was completely broken.

With no detailed information about the "new type of bomb" issued by the government, we did not know for about a week that it was actually the atomic bomb. We learned that the Soviet Union had declared war on Japan on the day of the Nagasaki atomic bombing. I was infuriated at our government, which still urged us to fight against the allied forces. We were injured, and suffering from a strange weakness with no adequate treatment. Food, clothes, information: everything was in shortage. Yet the government still shouted its slogan: "Ichioku gyokusai!" ("100 million people should meet honourable deaths; never surrender!") Who did the Japanese government exist for, I wondered?

Shortly after the explosion, many survivors noticed in themselves a strange illness: vomiting, loss of appetite, diarrhoea, high fever, weakness, purple spots on various parts of the body, bleeding from the mouth, gums, and throat, the falling-out of hair, and a very low white blood cell count. We called the illness "atomic bomb disease", and many of those who were only superficially injured died soon or months after. The lack of medical supplies and information about the after-effects of atomic radiation made it impossible to provide us with adequate treatment. First aid was all we could get.

Decades afterwards, I had a series of operations for cancer, which may be attributable to my having been exposed to radiation. However, I am not yet destroyed. With the blessing of gods and Buddha, I have been allowed to live. For the sake of those who were killed without mercy during and after the Nagasaki atomic bombing, and also for myself, I want to be able to survive for many more years. My physical being may be transient, but I believe that my spiritual being can remain undefeated. I wish sincerely that human beings will become wise enough to abandon all forms of nuclear weapons in the near future.