Dubbed Halo 3 Recon, a trailer for the game showed a UNSC special forces ODST (Orbital Drop Shock Trooper) emerging from a pod that blasted through the planet's atmosphere into a destroyed urban area.
The trailer said Halo 3 Recon will revolve around a new hero and new campaign and won't launch until fall 2009.
A new posting on Xbox.com said the Xbox 360 title will be a stand-alone expansion, and is "an intriguing side story that takes place during the terrifying events leading up to the Master Chief’s return to New Mombasa in Halo 3."
Microsoft also promised more stealth and strategic gameplay than in past Halo titles.
The company only revealed broad multiplayer details, saying Halo 3 Recon will employ new maps and expanded Forge options for Xbox Live Gold subscribers.
The game will be compatible with all of the community features incorporated into Halo 3.
Hit the link to download the trailer from Bungie.net.
In other news, Microsoft confirmed that the New Xbox Experience will launch around the world on November 19. It confirmed Tekken 6 and 99 Nights 2 for Xbox 360 and it said R-Type, King of Fighters and Metal Slug 7 would be Xbox Live titles.