By the tens of thousands they march through the streets of Pakistan, beating their backs and chests with chains and knives, mourning the murder of an Islamic figure killed 14 centuries ago today.
The scene on this 10th day of the Muslim month of Muharram is ghastly and provocative. The marchers, members of the 20 percent Shiite minority in Pakistan, blame members of the Sunni majority for the murder of their leader, Imam Hussein, the grandson of the prophet Muhammad.
On sidewalks and rooftops, their Sunni neighbors look on in fascination and disgust, not just because of the marchers' self-flagellation, but because many Sunnis consider Shias to be heretics and infidels.
"They are our opponents; they have changed all the basic beliefs of Islam," says Qazi Baha-ur Rahman, spokesman for the banned pro-Sunni party, Sepah-e Sahaba. "Beating and mourning and weeping is forbidden in Islam. That is why we don't do it. We prefer to follow the teachings of Imam Hussein rather than beating ourselves in his name."
It is this centuries-old dispute, pumped up by superpower politics, that has turned the 10th of Muharram into Pakistan's most dangerous day and presented the Pakistani government with its latest threat to internal security.
Already this spring, dozens of prominent Shiites many of them doctors have been assassinated leading up to Muharram. For Pakistan's President, Gen. Pervez Musharraf, the Shiite-Sunni fighting is just one more menace to control, along with fractious religious parties, militant groups, and Al Qaeda. Failure to halt this Sunni-Shiite violence will not only make Mr. Musharraf seem a weak ally in America's war on terrorism, but it will send a signal to foreign investors that Pakistan isn't ready for foreign-built factories and jobs.
"Lots of things are happening, and all of it is moving in the direction of deepening the faultlines in the Islamic world," says Ejaz Haider, news editor of the Friday Times, a political weekly based in Lahore. "Without addressing the basic causes of the present violence, there is no way it can be stopped."
The basic causes, religious and political observers say, have as much to do with the later stages of the 20th century cold war as with old doctrinal disputes.
After the 1979 Iranian revolution, US and Arab intelligence agencies helped created anti-Shiite militant groups to rein in any possible spread of Iranian revolutionary thought in Pakistan and other Islamic countries with Shia minorities. In the early 1980s, the concerns seemed well-founded, as Shiite students and businessmen marched by the hundreds of thousands in Islamabad.
But now, with the cold war over, the Sunni-Shiite divide seems to have gained its own momentum. Anti-Sunni and anti-Shiite parties have unleashed a spate of violence that has claimed more than 400 lives in the past five years.
For the most part, mainstream politicians applaud General Musharraf's rigorous efforts to bring sectarian parties under control. But some, like prominent Shiite politician Abida Hussein, say the government should have acted sooner.
"This gives the advantage to the jihadis to start getting active again," says Mrs. Hussein, a longtime senator for the center-right Pakistan Muslim League.
But while Musharraf may be able to jail the most fiery speakers from both sides, he can do little about 7th-century power struggles that created the Shiite-Sunni divide. According to Islamic historians, the trouble started in AD 579, when one of the last-surviving companions of the prophet Muhammad, the Amir Moawia, broke with tradition and selected his son Yazid as the future political and religious leader of the Muslims. The prophet's grandson, Imam Hussein, objected because, among other things, Yazid drank alcohol, kept dogs as pets, and delayed the times of the prayers. After some last-minute negotiations, Yazid's army killed Hussein and 71 of his followers on the banks of the Euphrates River in present-day Iraq. Since Hussein's family was not allowed to mourn for the following year of their captivity, modern Shiites who vow allegiance to Hussein and the Prophet's family mourn for them on the 10th of Muharram.
On the streets of Lahore, the police have managed to keep tensions cool by declaring the peak Muharram season as a national holiday. Some Sunnis say that it is not they, but the Shiites who create an atmosphere of tension, with their provocative calls to prayers over the loudspeakers and their processions. Others says that it is possible for Sunnis and Shiites to live together in harmony, but that these two groups can never reconcile.
"This difference is a fundamental in nature, and if it was possible to resolve it, they would have solved this 14 centuries ago," says Dr. Sarfraz Naimi, head of the Jamia Naimia University in Lahore. "But if Muslims can live with non-Muslims in peace, then there is no problem living with the Shias."