To assess the fractures dividing the Islamic world today, consider the clash that has brought Iran to the brink of war with Afghanistan's hard-line Taliban militia.
The saber rattling is creating a deep unease among many Muslims who fear further escalation of intra-Islamic conflict.
As foreign ministers today convene a meeting at the United Nations to defuse the crisis, analysts say the possibility of an Iran-Afghanistan war reveals much about two very different interpretations of Islam.
Taking part in the talks are Iran, Pakistan, China, Tajikistan, Turkmenistan, and Uzbekistan - along with Russia and the United States. Secretary of State Madeleine Albright and Iran's Foreign Minister Kamal Kharrazi will sit at the same table - the highest level contact since Iran's 1979 Islamic revolution.
The battle lines for the current crisis were drawn last month when 8 Iranian diplomats and a journalist were killed by Taliban forces during the takeover of Mazer-i-Sharif, stronghold of the northern anti-Taliban alliance.
Iran backs the opposition alliance and vowed revenge, deploying 70,000 troops along the border. To reaffirm that message, some 200,000 more Iranian soldiers are to begin exercises there this week.
At odds are two varying views of Islam and a host of political and strategic issues.
The Islamic Republic of Iran is a Shia Muslim state that backed the fractious opposition, including Afghanistan's minority Hazara Shiite group.
The mostly Sunni Muslim- and Pashtun-dominated Taliban are backed by Pakistan, and imposed their strict version of Islam - including extreme restrictions on women - on the 95 percent of Afghanistan now under their control.
An old fight revived
Highlighting the divide during prayers on Friday, the chief imam in Kabul called for holy war: "Every Afghan must be ready for a jihad against the Iranians," he said. "Iran, in conjunction with evil countries, is trying to prevent the installation of an Islamic regime in Afghanistan."
The call revives an old question for Muslims from Algeria to Egypt to Afghanistan: To what degree can jihad be waged against fellow Muslims?
"Islam has always had this incredible variety of expression, and the determining factor has always been the sword," says Reza Alavi, an Iranian analyst in Tehran and former managing editor of the Harvard Middle Eastern and Islamic Review.
For many Taliban ideologues, Shiites are considered a heretical branch of Islam and are not Muslim. "For some extremist Sunnis, killing a Shia is a way to get to Heaven, so a jihad against them is possible," Mr. Alavi says.
Iran often portrays itself as the chief protector of Shia communities around the world. So the fall last week of the last Hazara [Shia] stronghold of Bamiyan, in northern Afghanistan - coming just days after the London-based Amnesty International reported that thousands of people, many of them Shia, had been killed by the Taliban in the aftermath of the fall of Mazer-i-Sharif - heightened concern.
Officials on both sides make clear that they hope for a peaceful solution to the crisis, and most analysts consider any outright Iranian invasion unlikely. But Iran has been no less strident than the Taliban, and Supreme Leader Ayatollah Sayed Ali Khamenei has couched the crisis in religious terms.
"Don't allow this rigid-minded and heartless group to wage a religious war and spill blood which could - God forbid - spread to other parts of the Islamic world," Ayatollah Khamenei said last week. The "dogmatic and savage" Taliban were "alien from the shining teachings of Islam."
"So far I have prevented the raging of a fire in the region, which is not easily extinguishable," he warned. "But all should know that the threat is very huge and widespread, and very near."
Such statements cause alarm elsewhere, as well. In Egypt, for example, where Islamic extremists for several years waged a violent campaign against the secular government, the moderate Muslim Brotherhood is anxious.
"The killing of these diplomats is a big crime, it is not part of our belief in Islam," says spokesman Mahmoun al-Hodeibi in Cairo, whose group renounced violence in the 1970s. "But to make war would be a bigger crime. We refuse that any Muslim should fight any other ... Sunni or Shia."
Strategic aims, too
Though the religious divide is the most obvious difference, analysts say that equally important are spheres of Iranian and Pakistani influence and political dominance - issues that closely mirror the reasons for other Muslim versus Muslim conflicts.
Iran believes that the Taliban is spearheading a Pakistani-US-Saudi Arabian plan of controlling all Afghanistan, to provide unimpeded access for oil and gas pipelines from Central Asia.
Diplomats say the extensive Pakistani support for the Taliban is an open secret - and includes "volunteer" troops - while Iran's role in supporting the opposition has been more limited to arms and cash. The "official fiction," notes one Western diplomat, is that Iranian help is called "humanitarian aid." So the collapse of the anti-Taliban alliance was a major setback for Tehran.
Part of the Islamabad game plan may have been to create strategic depth in Afghanistan against its primary rival, India. But the Pakistani Army chief General Jehangir Karamat warned that a conflict could be "disastrous for Islam."
Pakistan says it would remain neutral in any fighting, but a strong pro-Taliban lobby would likely push for material and even volunteer support in the case of war. Sectarian violence against Shia targets in Pakistan last week left several dead and a mosque burned. Iranian diplomats were killed there in 1990 and 1997. Last year three Iranians were killed in Karachi, and five Iranians linked to the Air Force were reportedly ambushed.
Until the latest flareup, Iran and Pakistan had been working together as mediators in the Afghan civil war. The root of the differing views of Afghan militias date back to two events of 1979: Iran's Islamic revolution, and the Soviet invasion of Afghanistan.
Busy with overthrowing the Shah, Iran's new leaders did not focus on the drama across the border in Afghanistan, where the CIA and Pakistan, with Saudi funding, trained and equipped the Mujahideen "freedom fighters" against the American cold-war enemy.
Under orders from revolutionary leader Ayatollah Khomeini to "export the revolution," an Islamic battle against Christian Soviet invaders might have been appealing. But Iran was wary of its Russian bear neighbor - which could "mobilize 20 divisions along our common border, and roll into Tehran in 24 hours," says one analyst - and remained mute. And it was put off by the CIA role in the operation.
When Iran did engage, it backed the patchwork alliance that held power under President Burhanuddin Rabbani, until Taliban forces took Kabul in 1996. The Taliban emerged from religious schools in Pakistan in 1994, and their nearly complete takeover bid of Afghanistan has not lessened their zeal.
An array of conflicts
Though the Iran-Taliban tensions remain high, many other divisions simmer across the Islamic world:
* Iran was engaged in the last major war between two Muslim nations, during its war with Iraq during the 1980s. Some 1 million people were killed and wounded on both sides - a hard memory that analysts say has caused Tehran to think twice about getting trapped in a potential quagmire in Afghanistan.
Iran and Iraq are gingerly making amends - by releasing thousands of prisoners of war, and reopening the border for pilgrims - but the recent assassination of two senior Shia clerics in Iraq has rekindled mistrust.
* In Algeria, small extremist groups fighting the military government of President Liamine Zeroual often portrays themselves as Islamic fundamentalists. Their claim is rejected as a cover for violence by many Algerian clerics.
Horrible massacres in villages and bomb attacks in the capital, Algiers, have focused on civilians, most of them Muslims. The groups emerged after the military canceled 1992 elections that Islamic parties were set to win. The groups radicalized to violence, and widespread abuses by the security forces in response have alienated most Algerians.
* In Egypt, President Hosni Mubarak used repressive measures to break a cycle of extremist violence in the early 1990s that targeted the security forces, foreign tourists, and Coptic Christians. The secular state won when Islamic Jihad and the Gama'a al-Islamiyya declared a cease-fire last year.
* In Turkey, the all-powerful Army's mission for seven decades has been to preserve the secular nature of the state as enshrined by Mustafa Kemal Ataturk, father of secular Turkey. The Islamic Welfare Party was shut down earlier this year-only to reemerge under another name - but antigovernment violence is limited to the Muslim Kurdish Worker's Party (PKK). Though not an "Islamic" movement, the PKK has not shied away from killing fellow Muslims.
Despite this array of intra-Muslim conflicts, however, one reason for the deep anger between Iran and the Taliban may be simpler. The election landslide victory for the reform-minded President Mohamad Khatami last year was the starting point, but it has devolved into a fight between conservatives and moderates.
"Iran was trying to reconstruct the image of modern Islam as an open, liberal Islam," says Mr. Alavi. "It finds the Taliban embarrassing to Islam."