War and Peace

Our articles and data visualizations rely on work from many different people and organizations. When citing this entry, please also cite the underlying data sources. This entry can be cited as:

Max Roser (2018) - "War and Peace". Published online at OurWorldInData.org. Retrieved from: 'https://ourworldindata.org/war-and-peace' [Online Resource]

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.

I. Empirical View

I.1 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 that we have historical knowledge and an estimate of the number of fatalities of is shown in the visualization below.

The red circles visualize all conflicts in the Conflict Catalog (here) authored by Peter Brecke. Brecke's dataset contains information on 3708 conflicts, but in the more distant past it is still incomplete and for many past conflicts Brecke is either lacking an estimate of the number of fatalities or we can suspect that entire conflicts are completely unknown.

Global deaths in conflicts, since 14001


I.2 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

I.3 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

I.4 The 20th Century

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

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

I.5 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 in wars; in contrast, in 2007 (the last year for which I have data) the number of all war deaths was down to 22.139.

The detailed numbers for 2007 also show which deaths are counted as war deaths:8

  • Number of State-Based Battle Deaths: 16773
  • Number of Non-State Battle Deaths: 1865
  • Number of One Sided Violence Deaths: 3501
  • The total sum of the above is: 22139. This is the number of all war deaths on our planet in 2007.

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).

Number of annual war battle deaths by world region, 1946-20079

Click to open in Full Screen


I.6 The Share of War Deaths is Declining even Faster

The previous graph 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. The following graph therefore shows the battle deaths per 100,000 people per year. The figures are shown by type of conflict.

Rate of battle deaths in state-based armed conflicts by type of conflict, 1946-201310


Full screen view of the interactive chart Download the data visualized in the chart

I.7 The Number of Wars Increased until the End of the Cold War

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 number of wars increased until the breakdown of the Soviet Union and has been decreasing since then. Extrastate conflicts are colonial conflicts that ended with the end of colonialism. Interstate conflicts – wars fought between countries – have almost ceased to exist. As other wars are becoming rare, intrastate conflicts (civil wars) in some parts of the world remain.

Number of state-based armed conflicts by type, 1946-200711

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, 1950-200712

I.8 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.13

II. 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.

III. Data Sources

III.1 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

III.2 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.