The game has four difficulty levels with Veteran being the hardest. If you are playing the Xbox 360 or PlayStation 3 versions of the game, then Veteran is where you'll also be awarded the majority of the achievements this game offers. The difficulty level can be chosen at the end of the first mission, when you select a mission from the main menu and if you go to the "Lower Difficulty" option on the pause menu. The difficulty level affects the time limits in some missions and how often enemies will hit you when they shoot. You are advised on which difficulty level to take by the game at the end of the first level.
- Recruit
- Regular
- Hardened
- Veteran
This walkthrough goes through all 19 missions which are split up into two different special forces units: Task Force 141 and the US Army Rangers. To continue to the next mission, click the mission name in the footer.
For those who haven't completed the campaigns before, each new mission will be unlocked once the previous one has been accomplished. This stops you from missing out or skipping missions. The one exception to this is the mission No Russian. When you start the game for the first time, you will be asked if you would like to skip this mission and if you go to the pause menu while in the mission, you will have the option to skip it. This will not affect achievements or game completion.
This walkthrough will list some of the enemy intelligence pieces if the player goes near them. For the rest of the intelligence, see the Enemy Intelligence page.