Microsoft's just-revealed Halo 3: Recon, an expansion game that tells the tale of a new hero and is set before Master Chief's exploits in third Halo game, will release as a stand-alone title and not require the Halo 3 game disc for it to function, according to a Newsflash on the official Xbox web site.

To the delight of devoted fans across the world, at the Tokyo Game Show Microsoft debuted Halo 3: Recon, developed exclusively for Xbox 360 by acclaimed developer Bungie. This new chapter in the Halo saga lets you experience events leading up to the epic story told in Halo 3 through the eyes of a new hero in the Halo universe.

The stand-alone expansion, set to release in fall 2009, extends the award-winning Halo 3 experience with hours of new campaign excursions and multiplayer gameplay. -- Xbox.com

No mention by Microsoft or Bungie as to whether or not the game will be available as DLC, so for now be prepared to trek to the local game shop or visit your favorite online games retailer.

Here's a bit more information about the game, straight from the boys at Microsoft.

• All-new campaign content: The Halo 3: Recon campaign 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. Experience the fate of Earth from the brand-new perspective of a special forces ODST (Orbital Drop Shock Trooper), adding a unique outlook and new gameplay elements to the events that unfold in the trilogy's finale. While the feel of this new chapter greatly resembles that of previous Halo experiences, Halo 3: Recon will require you to employ more elements of stealth and cunning than ever before.
  
• Prepare to drop: Known for their courage, valor and, at times, insanity, ODSTs are among the fiercest UNSC soldiers, priding themselves on being the first unit deployed into hostile situations. While not as large or supernaturally gifted as their Spartan comrades, these "Hell Jumpers" more than compensate with their ferocious attitudes and unwavering nerve.
  
• Expanded multiplayer collection:No Halo experience would be complete without groundbreaking multiplayer content, and Halo 3: Recon gives fans more of what they love. With exclusive new maps and expanded Forge options, Xbox LIVE® Gold members will find more multiplayer content than ever before with Halo 3: Recon.
  
• Ever-growing community options: Enjoy all the great Halo 3 technological innovations, including Saved Films, screenshots, Campaign Scoring, and four-player co-op. All of the new multiplayer maps fully support the Forge editor, offering endless gameplay customization possibilities.