If I was going to get a crippling psychological condition brought on by the horror of ceaseless war, I would want it to be from Vietnam. It had all the coolest music, you see. Now, thanks to the hours I spent crouched in foxholes praying for my life in DICE's multiplayer-only expansion to their class-based online FPS, I'm as close as I'll ever get to suffering debilitating flashbacks. In that - and many other ways - Bad Company 2: Vietnam is an unbridled success.

Vietnam's warfare is not modern. It's ragged and frantic, and despite a smaller weapon-pool than its daddy, more noisy and lethal than Bad Company 2. I found no safe spots in the jungle or in the scree of open ground. Everywhere I ran, I heard the pop and whizz of super-fast metal. When I did manage to settle into a sniper spot - in a bush defending an objective, or up on a ridge in the superlative Hill 137 map - I'd regain a few seconds of blessed silence. Silence that became the harbinger of explodey death, as a counter-sniper on the opposing team brought his binoculars to his eyes, confirmed his target, and dropped a mortar strike through my skull.

Vietnam's maps are set up for modes identical to its parent game (which you'll need to play this £10/$15 expansion). Rush and Conquest mode return as the primary game types - the former has a team of attackers try and destroy a set of objectives through a changing map; the latter is a more standard capture-and-hold positions mode. Battles are filthy. At long range, bursts of machine-gun fire rip through undergrowth, highlighting channels of fire that the sensible avoid. But most fights happen up close, both parties firing from the hip and dying fast. The game's new flamethrower is a terrifying addition: less immediately lethal than you'd expect, it's a psychological game-changer. I stood in the back of a four man squad as we moved in on an objective through a trench. We rounded a corner, sights raised, to be confronted by a six foot jet of flame attached to a skinny Vietnamese man. Immediately our meticulous plans were fucked, and I was treated to the scarring image of three men backpedalling as fast as possible while their skin charred and their characters shrieked. It was harrowing, in the best possible way.

This combat ethos is echoed in level design. Where BC2's locales were clinical and modern, Vietnam's maps are mucky, messy, and missing a leg. New map Hill 137's first set of destroyable objectives are plonked in the midst of a lush jungle, with tight architecture and a lack of sight-lines for snipers. The second stage opens out into a yawning, smoking abyss of fire and tree stumps. It looks like some war poet's vision of hell, and completely changes the map's play-style, rewarding accuracy and planning. In the space of five minutes, Vietnam asks players to rethink class loadout and strategy.

The classes themselves haven't changed much, beyond a Vietnamification: the medic now has a syringe instead of defibrillators, and the assault class has a separate grenade launcher (with potentially the most satisfying 'thwunk!' noise in gaming). There's a slight problem with the engineer at the moment, as the lack of a tracer dart and a general dearth of vehicles means he's mildly less useful than in Bad Company 2. Still, his era-specific SMGs are an accurate and fast-firing choice that is potentially better suited to close-up duels than any other kit selection. All have their place, and all kill well.

During ten hours in the jungle, I've seen enough shit to ruin my psyche for life - my immediate response is still to helicopter myself back in for another tour of duty. DICE's take on the unwinnable war is a total victory.