Iraqi forces rolled unopposed through the huge Shiite enclave of Sadr City on Tuesday, a dramatic turnaround from the bitter fighting that has plagued the Baghdad neighborhood for two months, and a qualified success for Prime Minister Nuri Kamal al-Maliki.

As it did in the southern city of Basra last month, the Iraqi government advanced its goal of establishing sovereignty and curtailing the powers of the militias.

With the emergence of a political accord, the Iraqi military began to develop a new plan, which American officers learned about late last week. It assumed that Iraqi troops would be welcomed, or at least tolerated, by the residents. Instead of an assault through the roadside bombs, six battalions would drive in on parallel streets and set up checkpoints and search for weapons.

That plan was carried out on Tuesday and was uncontested.

So far, the Iraqi Army has been a winner. Iraqi commanders received, and sometimes rejected, advice from the American military. But in the end they were able to execute a plan that was very much their own.