2011 marks the 150th anniversary of what’s been called America’s second revolution, the Civil War. When it began in 1861, four million Americans were held as slaves by other Americans. When it ended four years later, more than 600 hundred thousand people were dead and many others never counted. It was a war, for and against, the right to secede and a war, for and against, the institution of slavery. Historians weigh in on how years of appeasement and compromise on slavery came to an end, the death and destruction unleashed by the war, and its meaning and memory today.