The great war - Harry Turtledove

Is it the war to end all wars - or war without end?

It is 1917, and the United States are fighting a war on two fronts. In the north, from the Pacific to Quebec, US forces in the air and on land are locked in battle against Canada and Great Britain. To the south, at the heart of a line that stretches from the Gulf of California to the Atlantic, General Custer intends to do what none of his predecessors have done - to smash through the Confederate lines in Tennessee.

Into this vast, seething cauldron plunges a new generation of weapons - submarines, barrels, attack planes, poison gas and flame throwers - changing the shape of war and the balance of power.

'The wizard of If.'Chicago Sun-Times

'The standard-bearer for alternate history.'USA Today