The militia that was once the biggest defender of poor Shiites in Iraq, the Mahdi Army, has been profoundly weakened in a number of neighborhoods across Baghdad, in an important, if tentative, milestone for stability in Iraq…

“The Iraqi government broke their branches and took down their tree,” said Abu Amjad, a civil servant who lives in the northern Baghdad district of Sadr City, once seen as an unbreachable stronghold for the group…

A month after Mr. Maliki’s military operation, strange things started to happen in Shuala, a vast expanse of concrete and sand-colored houses in northern Baghdad that was one of the Mahdi Army’s main strongholds. Militia members suddenly stopped showing up to collect money from the main gas station, a worker there said.

A member of the Shuala district council said: “They used to come and order us to give them 100 gas canisters. Now it’s, ‘Can you please give me a gas canister?’”