War and Peace

This entry presents an empirical perspective on war and peace.

We also published a data visualization history of human violence here on OurWorldInData.org which presents empirical data showing that we are now living in the most peaceful time in our species' existence.

Empirical View

The past was not peaceful

It would be wrong to believe that the past was peaceful. One reason why some people might have this impression is that many of the past conflicts feature less prominently in our memories, they are simply forgotten.

An overview of all the conflicts for which we have an estimate of the number of fatalities is shown in the visualization below.

The red circles visualize the conflicts listed in the Conflict Catalog authored by Peter Brecke. Brecke's dataset contains information on 3708 conflicts, but for the more distant past it is still incomplete. Brecke is lacking an estimate of the number of fatalities for many past conflicts, and we can suspect that the existence of many conflicts is unknown altogether.

In addition to the individual conflicts, the death rate from all conflict across the globe is shown. (The red line uses the Conflict Catalogue data, and the blue line uses a dataset constructed from PRIO and UCDP data).

Global deaths in conflicts, since 14001

Bubble and lines final 03

In Europe the second half of the 20th century was extraordinarily peaceful

The following Gantt chart shows the years in which European countries (or their predecessor states) took part in an international wars. Below the country-by-country visualization we see the sum (per half century) of all years in which European countries fought wars.

Years in which European countries took part in an international war, 1500-20002


Percentage of years in which the 'Great Powers' fought one another, 1500-20153

Percentage of years in which the great powers fought one another 1500–2000

Death rates from military conflicts in England, 1170s-1900s – Clark (2008)4

Death Rates from Military Conflicts in England, 1170s–1900s - Clark0

Wars and Other Atrocities in the Very Long Run

A list of 'Dictionaries or Encyclopedias of Wars and Battles' is presented by Peter Brecke in his article 'The Long-Term Patterns of Violent Conflict in Different Regions of the World'.5

'The 100 Worst Atrocities' over the last millennia – New York Times6

CLICK HERE to see the infographic in more detail.

The 100 Worst Atrocities over the last Millennia - New York Times [Data from Matthew White]0

The 20th Century

International battle deaths per 100,000 people, 20th Century – Acemoglu (2012)7

International Battle Deaths per 100,000 (20th Century) - Acemoglu0

War and Peace after 1945

The Absolute Number of War Deaths is Declining since 1945

The absolute number of war deaths has been declining since 1946. In some years in the early post-war era, around half a million people died through direct violence in wars; in contrast, in 2016 the number of all battle-related deaths in conflicts involving at least one state was 87,432.

The decline of the absolute number of battle deaths is visualized in the following graph that shows global battle deaths per year by world region. There are three marked peaks in war deaths since then: the Korean War (early 1950s), the Vietnam War (around 1970), and the Iran-Iraq and Afghanistan wars (1980s). There has been a recent increase in battle deaths driven by conflict in the Middle East, particularly in Syria, Iraq and Afghanistan.

Battle-related deaths in state-based conflicts since 1946, by world region
Click to open interactive version

Other forms of large-scale violence

The chart above refers only to battle deaths occurring in conflicts that involved at least one state on one of the opposing sides. For more recent years, we show these 'state-based' conflict deaths alongside battle deaths in 'non-state' conflicts (where two or more organisations are fighting but no state is involved), and also violent deaths in 'one-sided violence' (where there is only one organised aggressor, such as in genocidal violence).

We see that, in recent years, state-based conflicts form the majority of such deaths, though the genocide in Rwanda in 1994 stands out for its very high death-toll.

Violent deaths in conflicts and one-sided violence since 1989
Click to open interactive version

The Share of Battle Deaths is Declining even Faster

The previous two graphs showed absolute numbers, but as the world has seen rapid population growth (see our entry on global population growth), it is more appropriate to look at relative numbers. Here we show the battle death in state-based conflicts per 100,000 people per year. The figures are shown by type of conflict.

Rate of battle deaths in state-based conflicts by type of conflict, since 1946
Click to open interactive version

A Greater Number of Increasingly Less-Deadly Conflicts

As we have seen, the number of war victims varies hugely between different wars; whereas 1,200,000 died during the the Korean War (1950–1953), other wars had 'just' 1,000 victims. For this reason, statistics on the number of wars should not be considered without information on the size of these conflicts.

The following figure shows that the overall number of ongoing conflicts each year has increased, as compared to the immediate post-WWII period. This increase however only relates to civil conflicts within states. Conflicts related to the expansion or defence of colonial empires ended with decolonisation. Conflicts between states have almost ceased to exist.

Number of state-based conflicts by type, since 1946
Click to open interactive version

The increase in the number of wars shown before is predominantly an increase of smaller and smaller conflicts. This follows from the previously shown facts that the number of war victims declined while the number of conflicts increased. The decreasing deadliness of conflicts is shown in the following graph.

Deadliness of wars - average battle deaths per conflict by decade, 1950-2016

Deaths per battle 01

Ongoing Wars

Information on ongoing wars that is always up-to-date can be found at Wikipedia's List of Ongoing Military Conflicts.

After the documented decline of war, large parts of the world have now been peaceful for an unprecedented long period. Although wars are still fought, the world is now more peaceful than ever.8

Data Quality & Definition

Definition of War Most data for the period 1945 and later are taken from the PRIO/UCDP dataset. The following definitions quoted from the website of the Human Security Report Project apply:

  • A conflict is coded as a war when the battle-death toll reaches 1,000 or more in a given calendar year.
  • An extrastate armed conflict is a conflict between a state and an armed group outside the state’s own territory. These are mostly colonial conflicts.
  • An interstate armed conflict is a conflict fought between two or more states. An intrastate armed conflict (also known as a civil conflict) is a conflict between a government and a non-state group that takes place largely within the territory of the state in question.
  • An intrastate armed conflict becomes an internationalized intrastate armed conflict when the government, or an armed group opposing it, receives support, in the form of troops, from one or more foreign states.

For more information on definitions visit the website of the Human Security Report.

Data Sources

Long run perspective

Uppsala Conflict Data Program (UCDP) and Peace Research Institute Oslo (PRIO)
  • Data: Armed conflict data
  • Geographical coverage: Global
  • Time span: 1948-2008
  • Available at: Online here
Peter Brecke's Conflict Catalog
  • Data: 3708 conflicts, data on parties, fatalities, date and duration
  • Geographical coverage: Global
  • Time span: 1400 CE to present
  • Available at: Online at Clio Infra

After 1945

There are two major projects that gather on wars on a global scale for the post-war period and make their finding publicly available:

1. The Correlates of War Project

2. The PRIO, UCDP & Human Security Reports PRIO and UCDP collaborate to build the data set on wars. This data set is the base for the annual publication of the Human Security Project and for most of the data in this post.

Peace Research Institute of Oslo (PRIO)

Uppsala Conflict Data Program (UCDP)

Human Security Report Project

Data on Civil Wars

Data on on civil conflicts for the period 1945–99 was collected by Fearon and Laitin and can be found here.