Harry Turtledove 
Out of the Darkness 
Book Six of The Darkness Series

As the Derlavaian War rages into its last and greatest battles, allied nations manoeuvre for positions against each other in a postwar world. But before that time can come, the forces of Algarve, Unkerlant and their allies must clash a final time, countering army with army and battle magic with ever-more-powerful battle magic. In the midst of it all, the people the war has battered and reshaped must struggle to face their greatest individual challenges, as loves are shattered and found, terrible crimes avenged…and some journeys end forever.And the end of the war may not bring peace…