The name Nagasaki would never have appeared in the annals of the nuclear age had it not been for clouds and haze over Kokura, another medium-size coastal city on Japan's Kyushu Island, on the morning of Aug. 9, 1945.

"Bock's Car," the B29 bomber assigned to carry out history's second atomic attack, made three passes over Kokura, its intended target, but the crew was unable to get a visual fix.

So, low on fuel, the plane turned toward its secondary target, Nagasaki, an industrial center of 200,000. At first, Nagasaki was obscured by clouds too, but they parted and the crew made the decision to drop.

The bomb, drawing energy equivalent to 20,000 tons of TNT from about two pounds of plutonium, detonated 1,650 feet above the ground, billowing into a great, searing fireball.

"First, I saw the flash. An instant later, the winds began to blow, making a tremendous noise," recalls Tsukasa Uchida, who as a 15-year-old had been mobilized to work on torpedo gyroscopes in a Mitsubishi munitions factory 4,300 feet from the bomb's bursting point. He was showered with glass. The blast tore his shirt and shoes off and killed most of the 150 people on his shift.

Altogether, close to 75,000 people died instantly or soon after the blast, which obliterated 2.6 square miles. Over the years, an unknown number of others died of radiation-related diseases.

It was the final instance of massslaughter and a somewhat smaller one than Hiroshima, because the steep hills of Nagasaki helped contain the explosion. Five days later Japan surrendered.

At 11:02 this morning, horns, sirens and church bells sounded around Nagasaki to mark the precise 40th anniversary of the blast, as close to 24,000 people who gathered in the city's Peace Park fell silent for prayer.

Families of victims dedicated water at the park ceremony, in memory that thousands died pleading for a drink. Mayor Hitoshi Motoshima made another appeal for world disarmament. The names of 2,414 people exposed to the bomb who have died in the last year were enshrined.

Most school children in Nagasaki prefecture interrupted summer vacation and returned to class for a day of "peace study."

In many ways, it was a replay of rites conducted here every Aug. 9. Yet this city, now a rebuilt and scenic metropolis of 450,000, has no plans to stop the annual observances as long as there are nuclear weapons.

Historians have argued over whether the United States' cultural affinity with Germany -- they share a Caucasian, Christian heritage -- would have stayed Washington's leaders from using so terrible a weapon against that country's cities. It is pertinent to this discussion to note that the city that got Japan's second and final bomb is ranked among its most western and Christianized.

The Portuguese received permission to begin trading here in 1570.

The Dutch remained here even when the rest of the country was sealed off to foreigners in the mid-17th century.

When Japan reopened in the mid-19th century, more foreigners -- businessmen and missionaries -- arrived in Nagasaki. The churches and shuttered wooden homes they built gave parts of the city a European look.

"Fat Man," as the Nagasaki bomb was code-named, was supposed to fall on the city center and wipe out, along with large numbers of people, dock facilities, shipyards and factories. Misdirected, it fell two miles up the Urakami River on the main Christian quarter.

The devastation was so sudden and incomprehensible to residents that some Nagasaki Christians later invested the bombing with theological significance, seeing it as a test of Christians' capacity to maintain their faith in the face of suffering.

Ground zero was only 1,600 feet from the Urakami Cathedral, a Romanesque structure completed in 1913 and said to be the largest cathedral in the Orient. It collapsed like a house of cards, its statues scorched. Two priests and 24 parishioners inside were killed.

Shiroyama Primary School, located 1,600 feet from ground zero, was flattened, with 31 teachers and 1,280 students inside killed. Another 1,300 students died at the nearby Yamazoto Primary School.

Uchida's home, standing a few hundred feet from ground zero, was reduced to little more than its roof tiles. The pulverized bodies of his father, two brothers, a sister and sister-in-law were buried beneath it.