It is hard to picture what 51,000 dead and wounded soldiers look like. The scene came in the third year of the US Civil War at a crossroads town in Pennsylvania. When Robert E. Lee’s Rebel Army of Northern Virginia fled the battlefield at Gettysburg on July 4 1863 he left behind the conflict’s bloodiest tragedy, and the Southern cause was over. Now one hundred and sixty years later some Americans are calling for a civil war anew.