For the last year, Iraq has been consumed by violence that has pitted Shi'ite Muslims against Sunni Muslims. Some see the battle as religious, dating to the 17th century disagreement over who would succeed the Prophet Muhammad. Others say it is a modern day fight for political dominance.
Sunnis and Shi'ites have more beliefs that unite them than divide them. They share the same holy book, the Koran, and practice the five pillars of Islam, including the pilgrimage (Hajj) to Mecca.
Yet today in Iraq, they are fighting each other in a battle that Georgetown University Islamic History Professor John Voll says at its core is about the relationship between majority Shi'ites and minority Sunnis. The Shi'ites have been out of power and oppressed for a long time, while the Sunnis have been in power and do not want to share it.
"No politically dominant elite ever gracefully gives up power to a persecuted minority," he noted.
Professor Marius Deeb of The Johns Hopkins School of Advanced International Studies agrees.
"The conflict is really Saddamists versus anti-Saddamists. Unfortunately it took the form of the Sunnis, the old Saddamists, fighting the Shi'ites who come to be, unfortunately, pro-Iranian," he noted.
In February 2006, Sunni insurgents bombed a Shi'ite shrine north of Baghdad. That unleashed an all-out sectarian conflict in Baghdad and its surrounding areas that is still not under control.
"You have the great symbols of the Shi'ite tradition and the great symbols of the Sunni tradition become the words and symbols for mobilizing," said Voll. "This is why the destruction of the Golden Mosque in Samarra was such an important event. It represented an image and a symbol of the Shi'ite identity itself, and by destroying, it was a way of trying to continue to show the vulnerability of the Shi'ites."
Iraq's government is dominated by Shi'ite Muslims and many of them are closely allied with Iran. That concerns Iraq's mostly Sunni neighbors. In 2004, Jordan's King Abdullah warned of what he called the potential for a new Shi'ite crescent of governments and movements stretching from Lebanon to Iran.
Professor Deeb says the concern should not be so much about a Shi'ite crescent, but rather about the rise of militant Islam in all its forms.
"We can speak of a militant Islamic crescent which Iran and Syria are leading it with Hezbollah and Hamas and Islamic Jihad," he said. "They have the same agenda, an agenda which is destructive, unfortunately. Which will not lead to peace and reconciliation and end of conflict."
So what will bring the two sects together? Professor Voll says reconstruction of Iraq would be a good first step, providing areas where the two groups can cooperate.
"Economic reconstruction reduces the ability of Mehdi army and Sunni resistance militias to appeal to people," he said.
Professor Deeb says compromise and power sharing are important to reconciliation. Ultimately, he says, Iraqis need to discover again that they are part of one nation and let their national identity bind them together.