Gears of War 3 takes place around 18 months after the sinking of Jacinto at the end of Gears of War 2. The Locust, now without a queen to lead them, are struggling to survive after being forced to the surface. Human society on Sera has been reduced to small collections of people in an almost feudal or tribal system. Marcus Fenix and a small group of what remains of Delta Squad hole up and continue fighting.

There's a new enemy on the field: the Lambent, which have been seen in small numbers in the previous entries in the franchise, are a full force to be reckoned with now. These enemies are much more powerful than the Locust and will require concentrated fire to bring down. Lambent also explode when they die leading the Gears to develop new combat moves. For example, after chainsawing a Lambent foe, players will kick them away before the explosion, which can be used to take out other enemies.

This has created a three-way war between the humans, Locust, and Lambent, though we were assured that the humans will never team up with the Locust to fight the greater threat of the Lambent. All of this is playable with four players online in co-op. Player one will always control Marcus or Cole Train, while players two through four will control a varying cast of characters as needed for the narrative.

This game supports stereoscopic 3D.