Although snipers have been an essential part of successful urban warfare since World War II, the U.S. didn't set up an Urban Sniper School until May, 2001. The fighting in Afghanistan later that year did not require much urban sniping, but operations in Iraq over the past eight months certainly have. There's been a lot of on-job-training in Iraq, and CDROM versions of urban sniper training manuals have been hot items in American infantry units. Urban sniping, unlike it's rural counterpart, is much less about accurate shooting and much more about making the right moves in a more complex, and dangerous, environment. Out in the countryside, your average shot is going to be 400 meters, and shooting skills are critical at that range. But in urban areas, the average shot is a hundred meters. Shooting skills are still important, but it's simply easier to hit something at a hundred meters than at 400. The major problem for the urban sniper is where to set up, and what to look for. Scouting the battlefield is more work in urban areas, as there are more places for everyone, including enemy snipers, to hide. American troops have a big advantage with their UAVs and helicopters. Not only does the overhead eyes make it easier to sort out the urban battlefield, but you also tend to get a warning when the bad guys start moving in your direction. Another edge American snipers have is night vision equipment.
The Iraqis, lacking aerial reconnaissance and night vision gear, have to move very carefully, trying to stay indoors as much as possible. But this limits mobility, and American snipers quickly learned to set up shop aiming at those places where Iraqi attackers have to come out in the open. But this spotlights another problem with urban sniping; innocent civilians. If you see someone sneaking around carrying a rifle, you can be pretty sure he's your target. But not always, as Baghdad is still a burglars paradise and the coalition allows each household to keep one AK-47 for defense against the thieves. So what does a sniper do? In most cases you have to use your judgment. If the guy just seems to be checking the roof or alley for intruders, you don't shoot. If he appears to be taking up a firing position, he's toast.
American snipers also benefit from the popularity of computer databases. The PC revolution has the army keeping records of everything, and this is often useful. Snipers have always, as a matter of course, carefully recorded each shot, who was hit (or missed), plus when and where the shot occurred. A database of shots taken tells American snipers what the odds are of encountering various situations and that enables them to forget about the very rare events, and concentrate on the more likely developments. That usually means just shooting the guy carrying an AK-47, while wearing civilian clothes and moving along a roof, because the target is almost always hostile.
The sniper out in the countryside has to deal with spending hours, or days, in hiding waiting for a shot. In urban areas you face hours looking for the best shooting positions, and then moving into them and trying to keep the rapidly unfolding military operation (often a raid) sorted out while looking through your night scope for any suspicious activity.
U.S. infantry have found urban snipers to be a crucial weapon in dealing with unrest and hostile action. Iraqis trying to attack Americans have become much more cautious and reluctant as more American snipers are employed.