Welcome to Bad Company, soldier. You've been gone a while, and for some unexplained reason we've been shot through the past into the midst of the Vietnam war, so let's get ourselves refreshed by running over some of the ground rules. I'll have you up to speed in no time:

1) Know your place. You'll probably already understand how it's annoying when somebody who can't pilot a helicopter gets into one and then promptly flies it into the ocean. Why people insist on doing this is beyond me: I can't drive, so I would never even think about getting behind the wheel and nipping to Tesco for a pint of milk.

2) Medics are God. Put three medics together and they could probably tame a wild Zeus. If you see an enemy medic then shoot him immediately. Shoot other classes too, of course, just prioritise those bullets on those pesky healers. Do not let a clever pack of enemies revive and respawn on each other. Enemy medics are bad.

3) Battlefield: Bad Company 2 was really good, and everybody knows the game's soul lies in its delicious multiplayer. In reality that means you're trying to herd groups of 14-year old potty mouths to specific locations, but thankfully the four-player squad system meant you and a few mates could probably dominate the map if you kept your heads together. Even more so if two of you were medics - see 2)

First things first with Battlefield: Vietnam, then: there are five maps, not the originally suggested four. Five maps! For 1200 points! Compared to the kind of pricing structure other developers employ it actually sounds like an absolute bargain, but I'm sure suggesting something like that will invoke the ire of those old enough to remember when new Counter-Strike maps were provided for free.

Revealed from underneath the mysterious velvet curtain is Operation Hastings, a modernised port of a beloved map from 2004's Battlefield: Vietnam. The map is linked to a community challenge, and will unlock after players have amassed 69 million team actions - such as reviving, spotting and repairing. If it's anything like when Battlefield 1943 gave out a new map after 43 million cumulative kills then it should unlock within about six minutes of launch.

The fact Operation Hastings is updated version of a former map will probably have people on forums discarding the news and saying they're not actually getting 5 new maps, but they're probably missing the point: look up a YouTube video of the original Battlefield: Vietnam and you'll immediately appreciate how much effort DICE has put in to update Operation Hastings for the wonderful Frostbite engine.

On with the new, though: the four other maps are stunners. My personal favourite is Hill 137, which starts with some intense jungle battles before sweeping back into an ornate network of tunnels and scorched forestry - you can basically love the smell the napalm in the morning. Embers waft through the breeze, and thick plumes of smoke obfuscate vision and allow for raucous firefights.

As for how it all works, Vietnam nests itself within its own little sub-menu of Bad Company 2, and has its own separate progression trees: you won't just be able to sidestep your beefed-up profile into all of Vietnam's new gear.

While 15 weapons are provided across the game's four kits, some of them carry over - such as the M60 and 870MCS, albeit with the Vietnam equivalents looking grubbier and often wrapped up with cloth. Engineers get their lucky hands on the PPSh, the world's only submachine gun with onomatopoeic name. The Assault class gets an AK-47, a gun everybody who's even heard of video games already knows how to fire with deadly precision (watch out for the recoil) and the Medics get to murder everyone with an XM22.

But the most crucial new weapon is the flamethrower - it's expectedly devastating when used to clear out the many foxholes scattered around each map, but it's also quite funny to see somebody fire at you when miles away. The thing seriously knows how to throw flames, too, and combating somebody using one usually involves shooting wildly into the massive, all-engulfing fireball rather than popping off a tactical three-burst into their bonce.

It might startle you to find that red dot sights are out, too, which will certainly make my life harder. But it's Vietnam, so we'll have to make do. If it's any consolation, tanks will have radios tuned into Clearwater Credence Revival's Fortunate Son, along with dozens of other tracks.

All those Vietnam-era vehicles go down a treat, too. The iconic Hueys, patrol boats and M48 Pattons help make the 10-month-old game feel shiny and new and, alongside the meticulous briefing screens, add a palpable sense of atmosphere - Vietnam genuinely feels like more than Bad Company 2 with flamethrowers and foliage.

While I'm sure some people might lament the lack of UAV, the trade-off in other new features is totally worth it. DICE is producing one of the most lavish and generous DLC packs seen in years.

Battlefield: Bad Company 2 Vietnam will be available on Steam and the EA Download Store from December 18. Xbox 360 and PS3 owners will need to wait until December 21 to get the game from their respective online services.