Breakthroughs — Harry Turtledove

Is it the War to end all Wars-or war without end? What began in 1914 as a conflict in Europe, when Germany unleashed a lightning assault on its enemies, soon spreads to North America, as a long-simmering hatred between two independent nations explodes in bloody combat. Twice in fifty years the Confederate States of America humiliated their northern neighbor. Now revenge may at last be at hand.