From the end of the Cold War until 2010, war seemed to be going away. Inter-state warfare disappeared almost completely for a while. Civil wars continued, but at an ever-lower level, and came to be seen less as an existential threat than as a policy challenge to which regular instruments of public policy could be applied. A consensus emerged as to how those public policy instruments should be used, with the elimination— or near-elimination—of armed conflict as the goal.

Since 2010, however, this has unraveled. War is back. Armed conflict has been increasing steadily: the number of wars; the number of battle deaths; the number of terrorist incidents; the number of people displaced by violence. Almost everything to do with  war that can be reliably counted has been getting worse. Not yet catastrophically so, but to a degree and at a pace that has so far defied efforts to staunch it.