revolts, and fend off rivals. Throughout this era there were plenty of wars. For the period from 1400 through 1938, Brecke’s Conflict Catalog lists 276 violent conflicts in the Americas, 283 in North Africa and the Middle East, 586 in sub-Saharan Africa, 313 in Central and South Asia, and 657 in East and Southeast Asia.11 Historical myopia prevents us from plotting trustworthy trends in the frequency or deadliness of the wars, but we saw in the preceding chapter that many were devastating. They included civil and interstate wars that were proportionally (and in some cases absolutely) more lethal than anything taking place in Europe, such as the American Civil War, the Taiping Rebellion in China, the War of the Triple Alliance in South America, and the conquests of Shaka Zulu in southern Africa.
In 1946, just when Europe, the great powers, and the developed world started racking up their peaceful zeroes, the historical record for the world as a whole snaps into focus. That is the first year covered in a meticulous dataset compiled by Bethany Lacina, Nils Petter Gleditsch, and their colleagues at the Peace Research Institute of Oslo called the PRIO Battle Deaths Dataset.12 The dataset includes every known armed conflict that killed as few as twenty-five people in a year. The conflicts that rise to the level of a thousand deaths a year are promoted to “wars,” matching the definition used in the Correlates of War Project, but they are otherwise given no special treatment. (I will continue to use the word war in its nontechnical sense to refer to armed conflicts of all sizes.)
The PRIO researchers aim for criteria that are as reliable as possible, so that analysts can compare regions of the world and plot trends over time using a fixed yardstick. Without strict criteria—when analysts use direct battlefield deaths for some wars but include indirect deaths from epidemics and famines in others, or when they count army-against-army wars in some regions but throw in genocides in others—comparisons are meaningless and are too easily used as propaganda for one cause or another. The PRIO analysts comb through histories, media stories, and reports from government and human rights organizations to tally deaths from war as objectively as possible. The counts are conservative; indeed, they are certainly underestimates, because they omit all deaths that are merely conjectured or whose causes cannot be ascertained with confidence. Similar criteria, and overlapping data, are used in other conflict datasets, including those of the Uppsala Conflict Data Project (UCDP), whose data begin in 1989; the Stockholm International Peace Research Institute (SIPRI), which uses adjusted UCDP data; and the Human Security Report Project (HSRP), which draws on both the PRIO and UCDP datasets.13
Like Lewis Richardson, the new conflict-counters have to deal with failures of thinginess, and so they divide the conflicts into categories using obsessivecompulsive criteria.14 The first cut distinguishes three kinds of mass violence that vary in their causes and, just as importantly, in their countability. The concept of “war” (and its milder version, “armed conflict”) applies most naturally to multiple killing that is organized and socially legitimated. That invites a definition in which a “war” must have a government on at least one side, and the two sides must be contesting some identifiable resource, usually a territory or the machinery of government. To make this clear, the datasets call wars in this narrow sense “state-based armed conflicts,” and they are the only conflicts for which data go all the way back to 1946.
The second category embraces “nonstate” or “intercommunal” conflict, and it pits warlords, militias, or paramilitaries (often aligned with ethnic or religious groups) against each other.
The third category has the clinical name “one-sided violence” and embraces genocides, politicides, and other massacres of unarmed civilians, whether perpetrated by governments or by militias. The exclusion of one-sided violence from the PRIO dataset is in part a tactical choice to divide violence into categories with different causes, but it is also a legacy of historians’ long-standing fascination with war at the expense of genocide, which only recently has been recognized as more destructive of human life.15 Rudolph Rummel, the political scientist Barbara Harff, and the UCDP have collected datasets of genocides, which we will examine in the next section.16
The first of the three categories, state-based conflicts, is then subdivided according to whom the government is fighting. The prototypical war is the interstate war, which pits two states against each other, such as the Iran-Iraq War of 1980–88. Then there are extrastate or extrasystemic