The young militants

That October day Sara Mustafa, 14, a secular Sunni Arab, also trembled. The next morning, she covered up with an Islamic head scarf for the first time. The young fighters now controlled her life.

The Mahdi Army of Shiite cleric Muqtada al-Sadr is using a new generation of youths, some as young as 15, to expand and tighten its grip across Baghdad, but the ruthlessness of some of these young fighters is alienating Sunnis and Shiites alike. The fighters are filling the vacuum of leadership created by a 10-month-old US-led security offensive. Hundreds of senior and mid-level militia members have been arrested, killed or forced into hiding, weakening what was once the second-most powerful force in Iraq after the US military. But the militia still rules through fear and intimidation, often under the radar of US troops.

In late August, al-Sadr, the 34-year-old cleric, declared a freeze in operations, in part to exert more authority over his unruly, decentralised militia. Many followers stood down, so much that US commanders give al-Sadr some credit for a downturn in violence this year. But some militia leaders have ignored al-Sadr8217;s freeze, and their young, power-hungry foot soldiers may ultimately undermine the cleric8217;s popular appeal.

8220;We have to show people we are not weak,8221; said Ali, a 19-year-old Mahdi Army fighter in Tobji. Two years ago, Ali was unemployed. He recalled that he idolised his older cousins who were veteran Mahdi Army fighters.

Ali and his cousins once befriended Sunnis, Kurds and Christians. But after the February 2006 bombing of a Shiite shrine in Samarra, sectarian violence shattered Tobji8217;s tribal and social bonds. Suddenly sect was all that mattered to Ali, and the militia became his new family. He was 17.

Abu Sajjad, a 44-year-old former Mahdi Army fighter, remembered seeing a rise in disaffected, jobless recruits at the time. 8220;They were nothing before they joined the Mahdi Army,8221; said Abu Sajjad, who asked to be called by his nickname to protect his security. 8220;The Mahdi Army will protect them better than their tribes or their families.8221;

Ali, tall and slim with wavy black hair, spoke on condition that his full name not be used, fearing arrest by U.S. forces and retaliation by the militia. He is trying to leave the militia and has joined the Iraqi army, which he keeps secret from his comrades. In separate interviews, Sunni and Shiite residents said that Ali was a well-known Mahdi Army member involved in several attacks.

At the local al-Sadr office, recruits were given lessons in Shiite religion and Mahdi Army ideology, which centered on Shiite supremacy. The recruits were ordered to inform on anyone suspicious or breaking Islamic codes.

Today, more than half the militia here is under age 20. The new generation is heavily involved in the militia8217;s income-generating schemes. They sell the cars of kidnap victims and rent out the houses of displaced Sunnis. The militia also demands payments from generator men supplying electricity. Each month, youths collect 5,000 Iraqi dinars, or about 4, in protection money from every household.

Increasingly, the militia8217;s victims are Shiites. Tobji8217;s Shiite head of the local council, Abu Hussein Kamil, and another official were assassinated in August. Kamil, Ali said, had not given jobs to relatives of the militiamen and was suspected of collaborating with U.S. forces. 8220;He was hurting his own people,8221; Ali said.