In the opening menu, select 'Extra Content' and in the following menu, select 'Cheat Code' to bring up an entry field. Type the following codes:

Code - Effect:

MERCENARIES - Unlimited Ammo
HA2P1PY9TUR5TLE - Army Version
NICKWEST - Big Head Mode
SWEDISHARMY - Realistic Damage

When you start your objective, and a few of your men die, the game prompts you to press X to load from last save. Then it asks you to press Circle to begin a replay at last save point. Press Circle and you can fast forward the replay. Just before your men die on the replay, press Start. Scroll down the pause menu and select "Jump into replay". Then, stop your men from entering enemy territory.

This trick will help you through most of your missions by marking your enemies. Press R2 to bring up your GPS at any time then press Square. You will hear a woman's voice, and after about a minute she will mark the targets on your GPS. Be very careful, as there are some people that she cannot find.