Stand back to back, Troopers, and give the enemy no ground! The Covenant invasion of earth is almost upon us, and it’s going to take a great deal of teamwork to keep the Brutes at bay. In the second “Halo 3: ODST” ViDoc from renowned developer Bungie, “Halo” series fan favorite Sgt. Avery Johnson offers a detailed look at the game’s action-packed cooperative multiplayer experience, Firefight.

Firefight features ten hellish missions that will test your ability to work as a team as you and your squad mates take on waves of increasingly brutal Covenant baddies. Grim, game-altering skulls continually change up the game and force your team to adapt to shifting challenges. Surviving the Covenant onslaught won't be easy so why not bring a “Halo” icon to the fight; pre-order your copy of “Halo 3: ODST” now (visit http://xbox.com or http://bungie.net for participating retailers) and unlock Sgt. Johnson for use in Firefight!

In addition to the new ViDoc, Bungie and Microsoft recently lifted the curtain on Rally Point at Gamescom, a sprawling Firefight map located in the city of New Mombasa. More details about Rally Point are below:

• Sector 10 inside the city of New Mombasa has seen better days. The air is heavy with acrid smoke parted only by the constant arrival of enemy drop ships. Lucky for you, the crossroads that converge on the entrance into ONI’s Alpha Site offer up a textbook choke point. The Covenant has come to claim access. You and your squad of ODST’s are going to stop them at all costs.

The new “Halo 3: ODST” ViDoc is available for download today on Xbox LIVE Marketplace. Stay tuned for the final ViDoc, set to premiere ahead of the worldwide launch of “Halo 3: ODST” on September 22nd.