Aqua,
It's time for you to have a nice cup of STFU. The proper tactics and doctrine have already been explained to you. Unlike reading in a nice sterile, non hostile and quiet environment, a battle for real is neither text book, static or following the "ideal script".
There is no real time fully armed, fueled air response assets available on a 24 hr 7 day a week 5 minute arrival basis for every freaking troop or asset movement in the country. The air assets that are on station are there because of preplanned and implemented battle action plans. The same for ground rapid reaction forces.
It still takes time to get from the staging area to the area of combat and be able to determine in a compact urban environment where the good guys are and where the bad guys are. There is also a little thing such as aiming errors, blast radius and obstacles for the incoming rounds to get by to hit the target.
For the ground forces there is the concept of multiple ambushes. It doesn't take a tactical genius to determine if an ambush is started at point C it will innitiate a response from enemy forces at point D and that they will likely travel along route X. This means you can plan for a second and third or more ambushes along likely choke points to hit the reaction force before they are in a position to assist the first forces. The air and artillery assets are now split even further to try and support two or more active combat actions now going on.
The real word is not like some computer or video game. There are real penalties for taking improper actions or not following tactical doctrine that is written in blood from numerous combats in the past all over the world.
