The New Harmonies were original owners and settlers of Haven until the CoDominium decided any place that inhospitable would make an excellent dumping ground for political exiles, troublesome minorities and garden variety criminals. Over a year from Earth, by way of the old Bureau of Relocation deportee ships, Haven was the end of the line of CoDominium occupied space. During the Imperium, Haven was used as a recruiting ground for the Imperial Marines and became one of the first worlds abandoned when the war against the Sauron dominated Coalition of Secession got ugly.
Although humanity has annihilated the Sauron Homeworld, the cost was high: the First Empire is beginning its long spiral into a Dark Age and the secret of interstellar travel will soon be lost for centuries. When a shipload of Saurons bent on conquest arrive unexpectedly, War World goes from pest-hole to Hellhole.
Born of rebellion and civil war, cut off from the rest of humanity after the Secession Wars, Haven is bombed back to barbarism by the Sauron invaders. The Saurons, in fear of Imperial revenge, have vowed to cut Haven off from the rest of the Empire while they slowly absorb the superior human norms into their own perverted gene pool. Any and all who resist will die.
The Haveners should have been easy pickings for the superhuman newcomers. However, what the Saurons hadn't anticipated was the Haven is a world forever at war, each with all-and all against the Saurons.