This is the Second Formic War, the threat that led to the creation of the Hegemony, the Battle School, and the birth of Ender Wiggin.

A coalition of corporate and international military forces beat back the first invasion of Earth, and the devastation of much of our planet brought the nations of Earth together. But the war was not won. The single ship that did so much damage was only a scout ship. There is a mothership out beyond the Kuiper belt, and it's heading into the system, unstoppable by any weapons Earth can muster.