Over 50 years, the peace ceremonies held every year in the Peace Park have taken on a sacramental quality, and tomorrow's service - a half- century to the second after the dropping of the world's first atom bomb - will be conducted with all the hush and solemnity of a religious ceremony.
All week there have been marches by demonstrators dressed in symbolic white, their chants sounding more like calls to prayer than slogans condemning nuclear stockpiling or French tests. "The great achievement of the last 50 years has been the creation of Hiroshima and Nagasaki as holy places, almost Meccas of peace," said Mitsuo Okamoto, Professor of Peace Studies at the city's Shudo University.
But Hiroshima has other things in common with the world's holy cities: sectarian feuding, doctrinal battles and personal vendettas.
The Hiroshima Handbook lists 95 peace-related organisations from the Society of University Professors to Protect Peace and Freedom to the Mushroom Society. But chief among them are two, best known by their acronyms: Gensuikyo and Gensuikin. They are the Tweedledum and Tweedledee of Hiroshima.
Originally there was just one group, a loose association of journalists, trade unionists and citizens' committees, many of them victims of the atomic bomb. Left-wing activity was strictly controlled under the American occupation; the early organisation was "a guerrilla movement" in the words of one of its founders, Kiyoshi Matsue.
It was galvanised by the outbreak of the Korean War and the tests at Bikini atoll in 1954 during which Japanese fishermen were poisoned by radioactive fall-out. The following year the first Council Against A and H Bombs - Gensuikyo - was held in Hiroshima on the 10th anniversary of the bombing.
Less than a decade later, the group was rent by a dispute between factions led by the Japan Communist Party (JCP) and more moderate socialists. "The communist group defended the nuclear weapons held by the Soviet Union as justifiable, a defensive measure against the US, which was the only country to have used an atom bomb in war," said Professor Okamoto. "The others claimed all nuclear arms were evil and should be abolished."
"That is a total misunderstanding caused by Gensuikin propaganda," according to Dr Tomoyasu Kawai, of the Gensuikyo conference. The moderate group had, he said, abandoned their demands for immediate abolition of nuclear weapons favouring instead a gradualist approach.
The organisation split; beginning in 1964 there were two Hiroshima Councils Against A and H Bombs. Eventually, the breakaway moderates established their own handle, Gensuikin. There was a brief rapprochement in the Seventies, which fell apart when Gensuikyo announced its support of nuclear power.
"There are no substantive differences these days," said Professor Okamoto, who avoids both groups. "Only inertia keeps them apart, and the old personalities who used to excoriate one another in the Sixties and Seventies." This week the two sects have issued their own statements, mounted their own marches and run parallel conferences; they were almost indistinguishable in tone and content, but quite separate.
"This city's experience is so unique," said Professor Okamoto, ''it had the potential to become the leading peace movement of the world. But people see them squabbling, and feel alienated."