During the American Civil War the nature of conflict changed fundamentally. Both Union and Confederate Generals used trains to bring thousands of reinforcements, leading to longer and more frequent battles. It was the North who exploited the railroads the better - through geniuses such as Herman Haupt, who developed techniques of swift railroad construction - and destruction. The episode tells the story of the Great Locomotive Chase - an attempt by Northern spies to steal the locomotive The General. The conflict that divided America helped its unification - the lessons learnt in the war were used to build the Transcontinental Railroad that opened four years after the fighting ceased.