Conventions of war - Walter Jon Williams

The universe has fallen into bloody chaos now that the dread empire of the tyrannical Shaa is no more - at the mercy of the merciless insectoid Naxid who, freed from subjugation, now hunger for domination. But the far-flung human descendants of Terra have finally tasted liberty, and their warrior heroes will not submit. Separated by light-years, Lord Gareth Martinez and his one-time comrade and lover, the mysterious guerrilla fighter Caroline Sula, each pursue a different road to victory in tomorrow's ultimate battle - for the new order will be far more terrible than the old - unless one last, bold and desperate stratagem can hold a shattered galaxy together.