States involved in wars

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What you should know about this indicator

'1' indicates that the state participated in a war. '0' indicates that the state did not participate in a war.

States involved in wars
State was a major participant in at least one conventional war that year.
Jason Lyall - Project Mars (2020) – with major processing by Our World in Data
Last updated
September 21, 2023
Date range

Sources and processing

This data is based on the following sources

Project Mars. This dataset records new data on 229 unique belligerents in 252 conventional wars fought between 1800 and 2011. Project Mars introduces new data about these belligerents, including their level of prewar military inequality, and new measures of battlefield performance, including desertion, defection, and fratricidal violence. The latest version is Version 1.1. (2022-02-08).

You can find more details on the dataset in its notes at

Retrieved on
September 21, 2023
This is the citation of the original data obtained from the source, prior to any processing or adaptation by Our World in Data. To cite data downloaded from this page, please use the suggested citation given in Reuse This Work below.
Lyall, Jason. Divided Armies: Inequality and Battlefield Performance in Modern War (Princeton, NJ: Princeton University Press, 2020)

How we process data at Our World in Data

All data and visualizations on Our World in Data rely on data sourced from one or several original data providers. Preparing this original data involves several processing steps. Depending on the data, this can include standardizing country names and world region definitions, converting units, calculating derived indicators such as per capita measures, as well as adding or adapting metadata such as the name or the description given to an indicator.

At the link below you can find a detailed description of the structure of our data pipeline, including links to all the code used to prepare data across Our World in Data.

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Reuse this work

  • All data produced by third-party providers and made available by Our World in Data are subject to the license terms from the original providers. Our work would not be possible without the data providers we rely on, so we ask you to always cite them appropriately (see below). This is crucial to allow data providers to continue doing their work, enhancing, maintaining and updating valuable data.
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How to cite this page

To cite this page overall, including any descriptions, FAQs or explanations of the data authored by Our World in Data, please use the following citation:

“Data Page: States involved in wars”, part of the following publication: Bastian Herre, Lucas Rodés-Guirao, Max Roser, Joe Hasell and Bobbie Macdonald (2024) - “War and Peace”. Data adapted from Jason Lyall. Retrieved from [online resource]
How to cite this data

In-line citationIf you have limited space (e.g. in data visualizations), you can use this abbreviated in-line citation:

Jason Lyall - Project Mars (2020) – with major processing by Our World in Data

Full citation

Jason Lyall - Project Mars (2020) – with major processing by Our World in Data. “States involved in wars” [dataset]. Jason Lyall, “Project Mars” [original data]. Retrieved June 17, 2024 from