And now, with the new United Offensive expansion, Gray Matter Studios has taken Call of Duty and dialed it up to 11, adding thirteen new single-player missions and three new multiplayer modes. I imagine that the three key words in everyone's mind over at Gray Matter must have been "intensity, intensity, intensity" -- from the first mission, you're immediately pulled into scenarios and missions that seem familiar at first, and then explode into a scale that dwarfs the original game. Some of the ways that Gray Matter accomplishes this might leave passionate Call of Duty fans scratching their heads a little, but overall it adds something new and fresh to an already-classic title.

United Offensive follows the same pattern as the original, breaking its missions out into a three major arcs -- one for the Americans in Bastogne, one for the British in Holland and Sicily, and one for the Soviets in Kursk and Ponyri -- under which falls a number of smaller objectives. The mission types are generally the same as those with which you'd already be familiar if you'd finished the first game: attacks on fortified positions, defending those same positions after you've taken them over, sabotaging large installations, and rapidly escaping from sectors in which you're heavily outnumbered. What makes them different, though, is that the scope quickly expands from what you'd expect into an almost overwhelming situation.

Take, for example, a sequence that takes place early in the expansion, as you're asked to hold the line in the Bastogne forest. Following your commanding officer from trench to trench, you'll pick up your own weapon, a machine gun, a sniper rifle and a bazooka as you attempt to fend off an ever-increasing wave of German troops and armor. The pace is so quick, and the enemy fire so withering, that you'll barely have time to take aim before you have to change positions again, fighting Germans off the line or hoping quietly that you can take out the next Tiger tank with only one shot, so you don't have to leave cover for more ammo. If you survive, the sequence that follows -- illustrating why ground troops the world over love friendly air support -- is more than rewarding, and you might end up surprised at how much tension you'll have built up after only ten minutes.

Each arc offers a similar experience, to help you familiarize yourself with the new abilities and weapons that are available. The Russian and British arsenals have been beefed up to help them compare to the Americans, the Germans have a new carbine rifle, and all four playable armies now feature a canister-fed portable heavy machine gun. This last point might be the most interesting option (moreso than the surprisingly toothless flamethrower), and even though the opportunity to make use of it comes up rarely in the single-player campaign, it's still very satisfying to set up a nest and mow down anyone foolish enough to make a break across open ground.

Add to this some new scenarios, like the opportunity to run around a B-17 and fend off swarms of Messerschmitts or to hop into a Soviet T-34 and fight at Kursk in the largest tank battle in history, and you'll find yourself fighting in battles of a scale you hadn't imagined before.

This is United Offensive at its best.

It's possible that you might never notice United Offensive at its worst, if you're good enough at the game or you haven't set the difficulty too high. However, after you've been killed ten or twelve times in a particularly sticky spot, you begin to notice that United Offensive's fever pace is the result of some very tight, and almost constant, scripting. At one point in the American campaign, you run into a little shed with a hole blown through it, just opposite the door you're passing through. Should you pause to peek through it, you see an unoccupied yard with a few German jeeps and some crates; however, once you get to the exit, not three feet from the hole in the wall, at least five or six Germans will have appeared -- one of them only a foot outside the door. There are moments like these peppered throughout the game, ones that seem suspicious at first and downright frustrating as you play through them over and over.

The difficulty settings are occasionally comical, as well. When protecting your squadmates is an objective, they seem vulnerable to anything from a stiff breeze to foul language, but when they aren't part of the mission, you can actually hunker down and watch them take dozens of rounds, fall down, get back up again and keep fighting. Ironically, in those circumstances, the enemy actually seems to realize the futility of shooting at your squadmates, until you become the sole focus of their efforts. While it's gratifying to peek out a window and see an entire German squad (and their supporting tank!) waiting to shoot at you, it does tend to disrupt the suspension of disbelief. It's one thing to feel like every German in the war is shooting at you, but it's quite another for that to actually be true.

It's these minor details that keep reminding you that you're playing an expansion pack and not a fully-polished game. What a shame, too, because so much of United Offensive looks and sounds so good that you'd almost think you were playing a sequel. Gray Matter has done a tremendous job with the graphics, adding both a particle and a smoke effect that look very realistic until you're right up in the middle of them. The sounds are outstanding as well, and blend perfectly into the ambient backgrounds from the original title -- now when you hear the booming or rattling of distant explosions and gunfire, you can't be sure if it's just background noise or action taking place on another part of the battlefield.

This heightened sensitivity is especially effective in multiplayer, which include a number of new additions. Base Assault, Domination and Capture the Flag bring Call of Duty's multiplayer up to the level as its closest competitors, most particularly Battlefield 1942. Depending on the map and the server settings, all new modes offer the chance to bomb around in vehicles such as jeeps and tanks, as well as the ability to use heavy emplacements, like German .88 Flak guns. Also new is the in-game ranking system, which rewards the actions taken by players over the course of multiplayer games and issues them promotions. As players gain ranks, they get access to additional equipment and ammunition, items like satchel charges and binoculars, and finally the power to call in artillery strikes. This adds some interesting chemistry to multiplayer matches, and is occasionally very useful for telling the team players from those sniping from corners.

Call of Duty: United Offensive is definitely worth picking up if you had any kind of fun playing the original game, and especially if you're a hardcore fan. As long as you're prepared to make the jump from Band of Brothers-style detail to John Wayne style scale, you're going to love fighting for every inch of ground you take.