In 2014, a resurgent and bellicose Russia took over Crimea and fueled a civil war in Eastern Ukraine; post-Saddam Iraq lost a third of its territory to an army of hyper-violent millennialists; and the peace process in Israel seemed to completely collapse. In short, the post-Cold War security order that the US had constructed after 1991 seemed to be coming apart at the seams. David Kilcullen was one of the architects of America's strategy in...