Falling Torch — Algis Budrys

Twenty years after Earth is conquered by invaders from space, the exiled US government has a chance to reclaim their lost planet

2513 AD. For the past generation, since Earth was taken over by the Invaders, the US president and his cabinet have lived in exile on a planet in orbit around faraway Alpha Centauri. The Centaurian colony has become the center of the human race, reducing Earth to a backwater region in a sprawling foreign domain. But the banished American leaders still have a powerful yearning to return home. Now, President Ralph Wireman and his government finally have the financial aid and weaponry needed to retake their native planet. Wireman's son, Michael, is parachuted to Earth as a Free Terrestrial, where the military-trained warrior is thrust into battle not between human and alien, but among factions of outlaw earthlings who demand nothing less than his total surrender.
 
A novel about war, politics, and assimilation, Falling Torch also presents an incisive portrait of one man's aspirations of greatness and leadership.