One of the defining features of civil wars is their lack of civility. Once neighbor takes arms against neighbor, savagery often results. One of David Armitage’s tasks in Civil Wars is to define terms that are as hotly contested as the Gettysburg battlefield. He finds that victors tend to speak of “revolutions,” reserving “civil war” and “rebellion” for internal armed conflicts they deem as bad. By his terms, the American Revolution was a civil war, given that it often involved Americans fighting Americans, and the American Civil War is so called because the Union won (a Confederate victory might have resulted in something grander, maybe War for Southern Independence). The Harvard history professor writes with sharp irony and dense allusions on the recent past and near future. Because “civil war” has gained status in international law, the U.S. has become circumspect in pronouncing those two words given the legal obligations the term now entails.