Here is the story as I know it. After Togra left the planet, the world fell into disarray. Earth was overpopulated, and toxic fumes and nuclear waste polluted the planet. Huge domes were built for people to live in, but some were left behind. The people in the domes formed a large group called the JDF (Jovian Detention Facility), that dealt with the criminals and sometimes sent them to other planets to work. Soon, however, the JDF became almost a police force/government for the domes. The people left outside the dome adapted to their environment and became known as Sprawlers. The Sprawlers constantly launched raids against the domes to gather resources, while the JDF attacked back and sent groups of Sprawlers off to the prison planets.

Basically, for those of you who played Dark Reign 1, the Sprawlers are similar to Freedom Guard, while the JDF is similar to the Imperium. (In fact, the JDF was the group that chased Togra off planet and started the whole story of Dark Reign 1).