Infantry

To throw infantry into they mix, they need to be mobile and to use the infiltration tactics that almost broke WWI open for the Germans. On the attack, infiltrate. Get into position so that you can take a defensive position in a spot that makes life difficult for your enemy, then reinforce and support. I prefer to then consolidate the breakthrough, although the Germans did well enough in 1940 and 1941 with open flanks. It is very risky, however. The goal is to make the enemy have to attack you directly, so you can cut them up in the process. You don't want to be put into the position of a direct assault, yourself.