-Beat the game under the normal difficulty setting. This cheat must be enabled again if the player is killed, retires, or starts a new level.
-To do this easier, beat the game on under the Easy difficulty setting. Under the same profile, replay the intermission sequences under the normal difficulty setting, beginning with the "Brothers In Arms" scene then move to complete "Rendezvous With Destiny" to get the first two medals. Once you receive the medals for those two scenarios, quit, then play the "Victory In Carentan" intermission sequence under the normal difficulty as well. When you begin the game again, the "Infinite Ammunition" cheat will be now be accessible. The cheat must be reactivated after each chapter.