 Gears of War 2 takes place six months after the detonation of the Lightmass Bomb at the end of the first game. Though most of the underground army of the Locust Horde was destroyed, the explosion also caused much of the liquid Imulsion underground to vaporize, causing a fatal disease called Rustlung to spread among the diminished human population. After months of peace, the cities of Tollen and Montevado suddenly and mysteriously disappear underground, leading the Coalition of Ordered Governments (COG) to suspect the resurgence of the Locust. Soon after, the once impenetrable Jacinto, one of the last remaining safe havens for humans, begins to show signs that the same fate awaits it. To stop the fall of Jacinto, the COG responds with a large-scale counter-offensive against the Locust. Senior Producer Rod Fergusson says "In order to save Jacinto, [the COG] have no choice but to take the war to the Locust."
