EA DICE has confirmed that the upcoming expansion pack for Battlefield: Bad Company 2, entitled Vietnam, will feature a fifth map. It won't be available straight away though.
To unlock the map, players will be required to perform team actions - things like resupplying, reviving and repairing. Once 69 million actions have been performed across the Xbox 360, PC and PlayStation 3 communities, the map will become available for everyone to play.
The expansion pack is due out on the PC on December the 18th, and the 21st on Xbox Live and PlayStation Network.