Through the darkness - Harry Turtledove

As the war which consumes Dervelai drags on, the reserves of Algarve are ever more stretched. King Mezentio's armies become sucked into the huge landmass of Unkerlant. As more and more of the hated Kaunians are sacrificed for blood magic, conquered races are inducted into the Algarvian army, and their fighting edge becomes blunted. While at home, both men and women come to doubt the war and its purposes.
Harry Turtledove's blending of World War Two with fantasy has already gained enormous praise. From the once-proud Kaunians, who are herded into camps to die, to the brave yet doomed soldiers; from the generals who try to carry out their rulers' unreasonable demands, to the resistance movements which form in occupied lands, this series is a tapestry of the finest writing the genre can create.