What is the order of soldiers into battle during and after a fight?

I'm signing up for the military and really want to UNDERSTAND all my options. just wondering excactly how battle works, like first its cav scouts or spec ops special recon, then infantry and armor? When do snipers go in? then anyone come in after infantry? and whos in after the guys who are in after the infantry?? whats the order of unit deployment into small, medium, and large scale battles. Please include the roles of each military branch and roles of the units within them and also in what order. Thanks alot for the info everyone!! I appreciate it very much