[USMC Chuter]

To give a broader answer to your question, mech infantry generally rides into battle on Bradleys and, to a lesser extent, 113's. Once there, they provide a dismount capability to complete the mission on foot in concert with tanks, with the Bradley weapons systems providing additional fire support. Mech infantry divisions/brigades generally have an organic tank element. Armored divisions/brigades generally have organic mech infantry. The two combine to form a sort of armor/infantry combo.