Reported massacres of Shia soldiers and civilians in cities and villages captured by the radical Sunni Islamic State in Iraq and Syria (Isis) are meant to prompt Shias to retaliate against Sunnis, while Shia clerics are making Shia volunteers swear loyalty to their sect on the Koran before deploying against Isis forces.
The actions of both sides are fuelling a sectarian power struggle that threatens the very existence of Iraq. Although they share Islam’s basic beliefs and practices – the profession of faith, alms-giving, fasting during Ramadan, and the Mecca pilgrimage – a political divide opened between Sunnis and Shias after the death of the prophet Muhammad in 632.
Divide over succession
Sunnis felt that his successor should be elected from among his “rightfully guided” companions. Shias argued that Ali, the prophet’s cousin and son-in-law, and his descendants should succeed because they had a direct line to God.
Ali was anointed as the fourth caliph in 656 but was assassinated by fanatics in 661. His son Hussein was killed in battle at Kerbala in Iraq.
The anniversaries of these killings and the deaths of their successors are regularly commemorated by Shias, keeping alive resentment and reinforcing the 1,400-year-old split, which developed spiritual as well as political dimensions.
While 85 to 90 per cent of the world’s Muslims are Sunnis, three countries have majority Shia populations: Iran, Iraq and Bahrain. Lebanon and Pakistan have significant Shia minorities.
During most of the modern period, Iraqis of all classes bridged the sectarian divide. Tribes had both Shia and Sunni members and often wed children from the sects to cement unity. Relations were exemplified by close co-operation during the 1920 revolt against British rule. Both communities staged demonstrations calling for independence and an Arab government.
That spring, an iconic battle at the town of Fallujah involved fighters from both sects. (A national symbol, Fallujah was subsequently levelled by US forces in 1991, 2003 and 2004 and is now occupied by Isis and its Sunni allies.)
To combat secularism among Shias, senior clerics founded the Dawa party in 1957. During the 1970s, Dawa campaigned against the ruling Baath Party and, backed by Iran’s revolutionary clerics, launched an insurgency that precipitated the 1980-1988 Iran-Iraq war. During this conflict, Baghdad had the support of Sunni powers and the West. But during the 1991 and 2003 wars on Iraq, the US backed the Dawa-dominated expatriate opposition, which took power during the US occupation and systematically destroyed the frayed fabric of Shia-Sunni co-existence.
Sunnis were disenfranchised, denied entry to the army, police and civil service, detained and cleansed from mixed urban districts. Protests during 2012-2013 were put down violently by the Dawa- dominated government of Iraqi prime minister Nouri al-Maliki.
In response, Sunni tribesmen and former army and police officers have joined the Isis offensive.
A threatened attack on Baghdad could trigger a full-scale sectarian war in Iraq, prompt Sunni Saudi Arabia and Shia Iran to intervene on opposing sides, and lead to Sunni-Shia bloodletting across the Muslim world.