CoD4 takes an established set of gameplay ideas about how one can fit into an attacking group of soldiers all working together toward a common mission and brings it into the modern era. Instead of reliving old battles that took place more than half a century ago, CoD4 is all about a potential war that could take place in the near future. The story revolves around a group of Russian zealots who gain access to nuclear weapons. They arm elements of a Middle Eastern radical group and take over the government of Iran and fight a proxy war against the West. That's not really far fetched, if you ask me.
So, instead of fighting the Germans, you’re fighting the Russians and a radical army in the Middle East. There have been many discussions in blogs concerning whether this army is Iraqi or Iranian. Personally, I think it is an Iranian army. The nuclear blast that occurs at one point in the game definitely takes place in Iran. Although the city is not named, you can clearly see where it is on the map that is supplied during gameplay when the blast occurs.
As we have seen with other CoD releases, you get to play characters in multiple armies. In this game, you play as both a member of the British SAS and as a member of the United States Marines. The military unit you’re in makes a world of difference in how you play the game. In previous CoDs, when you switched armies to play different characters, the essential battle techniques remained pretty much the same. You might have a different rifle and a different uniform, but that was the biggest change. Tactics were essentially the same for all forces.
On the other hand, in CoD4, there is a major difference in how the SAS plans and conducts a battle compared to the missions you undertake as a Marine. The SAS battles are all about stealth and silenced weapons, sabotage and low intensity warfare. The US Marines, well, you know what they do. The Marines take on their enemies pretty much the same way they did during World War II except that they have much better weaponry today.
One very interesting example of how this modern warfare theme plays out occurs at the very beginning of the game. You start the game with a sort of boot camp session at the SAS base. Now if you have played any of the World War II simulators in the past, you’ll remember that they usually start out with a session in boot camp where you take a turn at the firing range, learn how to throw a hand grenade, and run through an obstacle course.
CoD4 throws all of that out the window and brings in a highly realistic and believable scenario where you participate in training for a specific mission using a plywood mockup of a freighter that you will be attacking in the first mission. So you practice your shooting and grenade throwing and maneuvers running through a map that, for all intents and purposes, is nearly identical to the ship that you are going to attack in the first actual mission.