You might want to read this first about the walls which I wrote back in 2004. Walls help, really. Pakistan is getting walled off. But here is a fascinating account of how a wall helped the Sadr City urban warfare situation. I quote:
Urban warfare has long been seen as perhaps the most difficult and demanding military task. Recent history features two approaches to it. The experiences of Russian forces in Grozny and U.S. forces in Fallujah illustrate one approach. In each case, noncombatants were told to evacuate in advance of the attack and anyone left was a de facto enemy fighter. Then these geographically remote cities were, in effect, besieged and then stormed, with attacks supported by massive firepower. The result: high casualties on both sides and rubbled cities.
An early priority was to stop the rocket and mortar attacks on the International Zone. JAM could launch these attacks quickly and almost at will. It simply required pulling a vehicle into a firing position, unloading the rocket and its firing rail, firing off the rocket, and driving back to a hide position: the work of minutes. U.S. forces quickly realized that the International Zone was at the extreme end of the 107mm rocket's range. Their solution was to push JAM fighters out of their firing positions and back into Sadr City. This approach did not stop JAM infiltration. The brigade then employed an innovative but straightforward approach: It walled off two neighborhoods south of Sadr City, including the one containing the Jamilla market where JAM got much of its resources. The wall consisted of T-wall sections, each twelve feet tall and weighing 9,000 pounds. (See photo above.) The wall became an impenetrable, nearly five-kilometer barrier that denied JAM what had been terrain and avenues of movement crucial to its operations. The fighting was particularly intense and required the brigade commander to commit Abrams tanks and Bradleys to dislodge JAM fighters and protect the soldiers building the wall.
As soon as the wall started to go up, JAM instantly recognized the threat posed to its operations and launched numerous attacks to stop its construction. The wall, in the words of one U.S. commander, became a "terrorist magnet." U.S. forces fought from a position of advantage and defeated the JAM assaults.
While the construction of the T-wall ultimately squelched the rocket attacks, by defeating JAM's fighters, U.S. forces waged an intense — and instructive — counter-fire campaign. Key to that campaign was giving the brigade commander direct access to ISR assets that he could direct almost immediately to identified firing locations without having to go through another headquarters. He could also pass intelligence rapidly and by secure communications down to the company level. He could attack enemy firing points around the clock with a formidable array of assets, including Apache helicopters, Air Force fighter aircraft, and armed Predator UASs. Brigade intelligence analysts honed their techniques over time and learned to follow JAM rocket teams to their source rather than attack them immediately. Then they could strike ammo dumps and more senior leaders, thus having a much more profound effect than they would by destroying a vehicle and a few foot soldiers.
The overall results impress. In about two months, U.S. and Iraqi forces crushed JAM, killing an estimated 700, won back significant numbers of the population, and re-established control of what had been an insurgent stronghold. U.S. killed in action numbered fewer than ten. Furthermore, the Multi- National Division Baghdad (MND-B) exploited the success of the combat gains in Sadr City with an intensive campaign of providing local security and reconstruction, all complemented by information operations.
In addition to the key lessons highlighted above, other key lessons emerged. First, persistent ISR, technical intelligence, and responsive precision strike are crucial to success, but they must be integrated at low levels. Second, ground maneuver was essential. It forced the enemy to react and enabled U.S. forces to seize control of the terrain south of Sadr City and to erect the barrier. Furthermore, capable indigenous forces were decisive in securing gains. Their presence signaled that Iraqis were in charge, not coalition forces who would eventually leave. Finally, forces must be able to transition from one type of task (counterinsurgency) to another (intense close combat) seamlessly and rapidly
Divide and conquer, in other words. It still works.