Darkness Descending by Harry Turtledove

Despite the title, Darkness Descending, the second novel in Harry Turtledove’s massive Derlavai saga, is far less pessimistic in tone than the introductory volume, Into the Darkness. Although the wars effects continue to be felt across the continent of Derlavai, and beyond, the actual battle sequences are generally limited to the Algarvian invasion of Unkerlant, told through only a few viewpoint characters.