Analysis: Shia-Sunni bitter divide

Iraq's largely Sunni Muslim insurgents have targeted the religious festival of Ashura in a series of attacks on the country's Shia Muslim majority.

The festival marks the anniversary of the martyrdom of Imam Hussein in the 7th Century.

It is a festival that defines Shia identity. It is all the more emotive this year, as Iraq's Shias celebrate victory in the national election.

By attacking Shia mosques and worshippers, the insurgents are taking revenge for that victory, attempting to foment civil war, and targeting a hated enemy.

It is another illustration that the rivalry between Shias and Sunnis is just as important for Iraq's future as the battle against foreign troops stationed in the country.

'Principal enemy'

"The Shia-Sunni competition for power has emerged as the single greatest determinant of peace and security in post-Saddam Iraq," argues Vali Nasr, an expert in Islam at the Naval Postgraduate School, in Monterey, California.

SHIA FESTIVAL: ASHURA

• Annual Shia festival commemorating martyrdom of Imam Hussein
• Hussein, grandson of Prophet Mohammad, killed at Karbala by army of Caliph Yazid in 680
• Faithful strike themselves with chains and swords to atone for Hussein martyrdom
• The murder 19 years earlier of Ali, Hussein's father, gave rise to the central schism in Islam between Sunni and Shia

What is Ashura?

In pictures: Baghdad blasts

The bitterness of the divide is expressed most starkly in a letter, believed to have been written by militant leader Abu Musab al-Zarqawi, intercepted last year.

He described the Shias as "the lurking snake, the crafty and malicious scorpion, the spying enemy and the penetrating venom".

For militant Sunnis, like Zarqawi, the Shia are enemies not just because of their current alliance with Washington. They are the principle enemy.

Bitter rivalry

Sunni and Shia have been bitter rivals since the two sects of Islam parted company in the 7th Century.

But the intensity of the modern conflict dates from the Iranian revolution of 1979.

Militant Shia Islam in Iran was eventually mirrored by militant Sunni Islam in the surrounding countries, most notably Saudi Arabia.

The battle between Shia and Sunni has been fought, with many deaths over the last two decades, in Pakistan, Afghanistan and many other countries of the region, not to mention Iraq itself.

In Iraq, vicious repression of the Shia majority by Saddam Hussein kept the Sunni minority in power, even though Arab Sunnis are estimated to make up only about 20% of the Iraqi population.

Dilemma for Shias

Now it is the turn of Iraq's Shias to take power, for the first time since the Ottoman conquest of the area in 1533.

They make up some 60% of the Iraqi population.

But their victory in the election was guaranteed by two factors: the united list of candidates they assembled with the support of the Grand Ayatollah Ali Sistani and the Sunni boycott.

So now it is up to Iraq's Shias whether they respond to the extreme provocation of these attacks, or whether they work with the more moderate elements of the Sunni Muslim community in assembling a government and building a united future for Iraq.