Is war declining – and why?

The article reviews and assesses the recent literature that claims a sharp decrease in fighting and violent mortality rate since prehistory and during recent times. It also inquires into the causes of this decrease. The article supports the view, firmly established over the past 15 years and unrecognized by only one of the books reviewed, that the first massive decline in violent mortality occurred with the emergence of the state-Leviathan. Hobbes was right, and Rousseau was wrong, about the great violence of the human state of nature. The rise of the state-Leviathan greatly reduced in-group violent mortality by establishing internal peace. Less recognized, it also decreased out-group war fatalities. Although state wars appear large in absolute terms, large states actually meant lower mobilization rates and reduced exposure of the civilian population to war. A second major step in the decline in the frequency and fatality of war has occurred over the last two centuries, including in recent decades. However, the exact periodization of, and the reasons for, the decline are a matter of dispute among the authors reviewed. Further, the two World Wars constitute a sharp divergence from the trend, which must be accounted for. The article surveys possible factors behind the decrease, such as industrialization and rocketing economic growth, commercial interdependence, the liberal-democratic peace, social attitude change, nuclear deterrence, and UN peacekeeping forces. It argues that contrary to the claim of some of the authors reviewed, war has not become more lethal and destructive over the past two centuries, and thus this factor cannot be the cause of war's decline. Rather, it is peace that has become more profitable. At the same time, the specter of war continues to haunt the parts of the world less affected by many of the above developments, and the threat of unconventional terror is real and troubling.