NAJRAN, Saudi Arabia — Among the ruins on the edge of this ancient oasis city are deep trenches littered with bones. That, local people say, is all that remains of one of the great atrocities of antiquity, when thousands of Christians were herded into pits here and burned to death by a Jewish tyrant after they refused to renounce their faith.

The massacre, which took place in about A.D. 523, is partly shadowed by myth and largely unknown to the outside world. But it has become central to the identity of the people now living here, who mostly belong to the minority Ismaili sect of Islam. The Ismailis, widely reviled as heretics by Sunni Muslims both here and abroad, see the oppressed Christians of ancient Najran as their literal and figurative ancestors in a continuing struggle for recognition by the Saudi state....

Historians offer a somewhat different account of what happened here, though the facts remain sketchy. A Jewish king named Dhu Nuwas did kill a large number of Christians in Najran in 523, a century before the birth of Islam. But the notion that they died because they refused to renounce Christianity appears to be mythical, said Christian Robin, a French archaeologist. And the claim that they were burned to death en masse — with its eerie Holocaust overtones — also appears to be untrue, Mr. Robin added; most were killed by sword. Nor is it clear that the Koranic passage refers to what happened here....