EFPs are the most terrifying IEDs ever designed. They fire molten copper plates faster than bullets at passing vehicles which cut through Humvees and tanks as though they were Jell-O.

"Do you know who they're buying them from in Iran?" I said. "Are they buying them from the government?"

"Who knows?" he said. "Maybe if we did know we could do something about it."

My Spanish colleague Ramon Lobo from El País in Madrid co-interviewed Major Humphreys with me.

"I think they get them from the Revolutionary Guards," he said.

"Right," I said. "Which is, of course, part of the government."

"According to Iraqi media," Major Humphreys said, "they're getting support from the al Quds Force."

The Quds Force is basically the special forces branch of Iran's Revolutionary Guards. Its commanders report to "Supreme Leader" Ayatollah Khamenei. Their mission is the arming and training of guerrilla and terrorist organizations around the Middle East - especially in Lebanon, Iraq, and the Palestinian territories.

"One thing you'll notice on the map," Major Humphreys said, "is that all roads point toward the Green Zone."

"The roads were perfect launching positions," he said. "These guys built their launching pads, they had engineers who knew what they were doing, they knew the right angles, and they knew where they were going to launch from. They were very well-trained. Al Qaeda is mostly a bunch of thugs who are paid by people outside Iraq just to wreck havoc by dropping poorly made IEDs. They're not very well organized. But the Shia militias are used to working in a military manner with senior commanders, and with training sponsored by international forces in Iran. They have a sense of leadership. These guys knew what they were doing. They were launching these rockets from roads that are perfectly lined up to the Green Zone every day."

Not only did the Shia militias buy their rockets from Iran, they paid with cash extorted from businesses in the Jamilla market. So the Iraqi government had yet another reason to want them out of Jamilla.

"It's hard to block this whole area off," Major Humphreys said, "because there are so many nooks and crannies that people can get in and out of. So we started building the wall. And it took us about two months. It's a three-mile wall on what we call Route Gold. And it worked. As soon as the last barrier went in, the violence in south Sadr City almost completely stopped."

Mahdi Army senior leaders fled as soon as they lost their funding, resources, and territory in and around the market. Some went to Iran. Others went into hiding somewhere else in Iraq. They wanted to get back in, but they couldn't. So they made a face-saving deal with the government. They "agreed" to stay out of Sadr City entirely as long as American soldiers stayed on the south side of the Gold Wall.