A large asteroid has wiped out all life on Earth. As head of one of the two last outposts of humankind, your task is to rebuild the human race. All the rich resources of the solar system are at your disposal, but there is also the problem of the Martian outpost: they believe themselves to be the superior offshoot of humanity, and they will not take too kindly to your attempts at revival.
So while you are busy harvesting minerals and establishing new colonies, you must also build up defenses, and perhaps even a fleet, to counter the inevitable assaults. Who knows, one day you may even be able to return to the rock that was once Earth.