Poul Anderson 
Fire Time 

Anu, red giant companion-star to Bel and Ea, was relentlessly approaching Ishtar — scorching the land, forcing the barbarians of the North ever southward away from the Inferno. Fire Time was fast confronting the planet; civil war broke out as the Tassui led their forces against the army of the Gathering in a desperate struggle for survival.The Gathering anxiously awaited help from the human colony in Primavera. Jill Conway and other colonists like her hoped to save the civilisation of Ishtar and they relied on the Navy of the Federation of Earth to do so. But now the Federation was engaged in its own was, an interstellar war that seemingly had no end. And no end meant no help of Ishtar…