Many troops coming to Iraq thought they had their drills down pretty good. But they found that a little more speed could be a life saver. Fire teams (4-5 troops) can sometimes be seen practicing in their bases. Even marines aboard their amphibious ships, on their way to Iraq, will take over small portions of the ship and practice for hours, in the hope of shaving a second or two off their time. The moves become automatic, and buy you a few seconds for when the unexpected does happen, and you need a few seconds to get out of it alive.
Even non-combat troops have been introduced to battle drills in Iraq. Every soldier and marine gets some exposure to these drills in basic training. If you are assigned to a combat support unit (in a combat unit), there is some refresher training. Just in case. But in Iraq, it became a matter of life and death how well, and how fast you can open fire from inside a truck, or get out of the truck and get in the best position to fight back. The army opened a special school in Kuwait, where non-combat troops can learn how to survive, when they come under fire while driving supply trucks through dangerous areas.
New tactics have been developed as a result of so many troops getting involved in combat. When speed is needed just to get near the building to be cleared, a hummer will be used. The vehicle can approach a building more quickly, and quietly, than an M-2 Bradley. The Stryker, because its on wheels, is almost as fast, and the Stryker brigades have used their armored vehicles speed and low noise level to quickly get close to targets, before the troops jump out and into the building. Even getting out of a vehicle quickly can be improved with practice. Nothing like a few close calls to generate a lot of enthusiasm for practice, lots of practice.
In combat, speed kills. Or saves lives if you happen to be the faster team. In Iraq, American troops have learned the value of drills (exercises that increase speed). These drills are the precise sequence of movements you make in combat situations. The scariest ones involve clearing buildings. You want to hit uncleared rooms so fast that any enemy fighters inside wont have time to react, or will react too slowly to be effective. These same drills have been used to good effect in the hundreds of raids conducted every month. In most cases, there is no one waiting with a weapon, but if there is, it is rare for them to even get a shot off. Speed also limits the ability to hide weapons or documents.