Call of Duty: United Offensive gives you thirteen new missions in the single player game, and once again you will play the game from different perspectives. In the first campaign you will play a member of the American 101st Airborne on patrol near Bastogne when you find yourself in the middle of a massive German push -- The Battle of the Bulge. You continue with that character through combat in the woods, house-to-house fighting, defensive and offensive sieges, infantry and tank combat up to the recapture of Noville. You will also play a British gunner in a B-17 bomber fighting off German Messerschmitt fighters from a turret as your plane flies through flak on a mission over Holland. This has to be one of the most intense moments in the game, and provides a nice break from the squad-based combat featured in the original Call of Duty and most of the other missions in this expansion. You also get to play a British elite operative sent in to eliminate command-and-control centers and defensive positions on Sicily prior to the British invasion, and then escape in a stolen motorcycle and sidecar to the waterfront where a boat is waiting to try to break you and other operatives out of the heavily patrolled waters. After completing that stage you then get to play a Russian soldier in the trenches and town fighting along the eastern front, who gets drafted into a T-34 tank for the Battle of Kursk against German Panzers, Tigers, and Elefant tanks and anti-tank weapon equipped infantry. As you progress through all three campaigns you will have access to more weaponry than in the original, including portable machine guns and flamethrowers, and experience more vehicle combat as the gunner on motorcycles, jeeps, planes, boats, or tanks. You also get to experience weather effects during combat, with decreased visibility due to rain and snow. The British missions are a nice break from the trenches, but the American and Russian missions have so many soldiers on the field that you truly feel the epic nature of World War II.

There are also some new abilities added to the game. You can sprint for short distances, which is incredibly helpful for moving from one patch of cover to the next in the larger battles. You can also "cook off" a grenade, holding it for a few seconds after pulling the pin, so that it explodes sooner after you throw it.

I have mixed feelings about the AI for the single-player missions. On the one hand, your foes are doing their best to outflank and kill you, and your squad-mates are helpful. However, the foes pick you out as their priority target, and your squad-mates don't always respond if they aren't being shot at. This increases the difficulty of the game, but in some missions it was downright annoying to die while your squadmates might as well have been having afternoon tea. I'd love to be able to issue commands to my squadmates, but perhaps we'll see that in Call of Duty 2.

The other AI issue I wasn't thrilled with was the instant-death artillery strikes. In some missions, if you don't follow the somewhat unclear path that the designers have laid out, or if you move too slowly, you are apt to get hit with artillery fire or an air strike that sends you to the reload screen. The mission at the bridge of Ste. Foy is particularly bad for this. It took me many tries to get past that mission, and I had to walk away from the computer several times out of sheer frustration at that one mission.

One other AI change from the original is the never-ending spawn point. In several missions you will face unending waves of Germans until you advance far enough to trigger the event that turns off the spawn points, leaving you to fight off wave after wave of Nazis. Of course, your ammo and health packs are not unending, so this can be disastrous until you figure out what is going on and make that push. Despite these three AI limitations, the game is still enjoyable, so don't let these drawbacks keep you from experiencing this expansion.

The multiplayer game has been vastly improved. In the original Call of Duty the multiplayer mode was an interesting diversion. In Call of Duty: United Offensive the multiplayer game is a game in its own right. This is largely due to the new combat modes for multiplayer gameplay and maps that are more well-thought out than in the original. Being able to take control of jeeps and tanks raises this part of the expansion to a whole new level though, and creates many new tactical situations to play through. You can also make use of all the new weapons in multiplayer mode, as well as the opportunity for higher ranked members of your team to call in airstrikes using binoculars. The addition of base defense and capture the flag modes, both staples of multiplayer games, to United Offensive's multiplayer mode widens the scenario options greatly as well, but the Domination mode is just plain intense. In that mode, you have to capture and hold all five or six zones on the map. Compared to the original, the multiplayer game is a whole new experience, and is worth purchasing the expansion for even without the 13 new single-player missions.

If you have played and liked Call of Duty, the United Offensive expansion pack is well worth it. The variety of mission types and greatly improved multiplayer combat more than compensates for the few AI issues.