While American troops received a lot of urban warfare training before going into Iraq, many of the soldiers and marines observed, after doing some street fighting, that the training was not stressful and unpredictable enough. This is a complaint that goes back to World War II (when extensive army surveys of combat troops revealed this little gem, and many others that keep reappearing even today.) But the bureaucracies that set up the training tend to slow things down so they can make sure everything is being done right. What is often lost is that the additional high speed run-throughs, with instructors throwing in unexpected items (a grenade, or additional fire from an unexpected direction) provides an essential realism element. It's another example of the need to "train as you fight and fight as you train." Or, to put it more bluntly, if the training doesn't scare the troops and stress them big time, it's not working.