It starts fast, speeds up, and just about never slackens the pace. Building on the outstanding Call of Duty, Activision's United Offensive expansion pack brings 13 fresh missions, three new multiplayer modes on 11 original maps, and a decent mix of new weapons, vehicles and troop types. Divided into US, UK and Russian sections, the single-player campaign is fought across excellent environments amidst terrific special effects and a solid but heavily scripted story-line. Veterans will jump straight in where they left off, and the intuitive interface means that newcomers should have no trouble at all. The large scale battles that made Call of Duty so popular are back in most missions, and developer Gray Matter has squeezed everything it can from the aging Quake III engine.

New weapons include Browning Light Machine Guns, M1A1 Bazookas, Tokarev SVT-40 bolt action rifles and the dear old Webley pistol; supported by Flammenwerfer 35's, satchel charges, smoke grenades and the chance to take over stationary weapons like heavy machine guns and light artillery. The new controllable vehicles (disappointingly rare in single-play) include tanks, trucks and jeeps, and players will welcome the simple driving controls. United Offensive retains the original's clean on-screen interface and most actions are straightforward.

Surprisingly, nothing obvious seems to have been done with the average friendly AI, and swarm attacks still seem to be the order of the day for the enemy. It doesn't affect multiplay, but improved AI would have strengthened the single-player game considerably.

Aside from the new maps and modes, multiplay brings some nice tweaks to an already strong system. A ranking structure that awards special abilities like scouting binoculars, explosive skills and artillery strikes has been added, and the new overhead map option aids team cooperation and improves situational awareness in what are generally frenzied environments. Call of Duty: United Offensive certainly brings more to the multiplayer experience than single-player, but it's a worthwhile update to a great title.