The European Union and its predecessor organisations are frequently cited as being a causative factor (rather than simply a correlative) in the relative peace experienced by Continental Europe post-1945.

Indeed, the stated intention of the progenitors of the European Project was to make another large-scale war less likely - but that doesn’t mean their arguments had merit or continue to do so.

So what evidence is there that the European Union (or its predecessors) has had a positive impact on the peaceability of the Continent?

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    Could you be more specific as to what exactly you would regard as evidence?
    – redleo85
    Oct 30, 2018 at 12:03
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    In your question you refer to causes and not correlations, so "facts indicating" does not seem enough. There are studies showing that countries with high trade volumes have less military conflicts among each other. But that would be correlational. Or is this what you're looking for?
    – redleo85
    Oct 30, 2018 at 12:29
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    Since we don't have a 'control' Europe that never had an EU it'll be hard to prove any causation. Someone may be able to compare EU western Europe with Warsaw Pact eastern Europe, but there would be a lot of factors to account for.
    – Giter
    Oct 30, 2018 at 13:24
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    @Ben: It's likely that the EU is at least partly responsible for peace so there's probably some causation, it's just that we wouldn't be able to prove if any alternatives would have been more or less peaceful: saying "EU is a reason for peace" is probably true, but "EU is the reason for peace" probably isn't.
    – Giter
    Oct 30, 2018 at 13:58
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    Fair enough. I suppose the more interesting question is whether some element characteristic of the EU, rather than a more typical FTA, has had a causative relationship to peace.
    – 52d6c6af
    Oct 30, 2018 at 14:09

2 Answers 2


It is probably not possible to prove a causality as politics is not a natural science where experiments can be repeated.

The European Union and its predecessors implemented multiple measures, which in general reduce the likelihood of violent conflict. One main point is to reduce hostility between the two central European powers France and Germany. Since the mid 1700s there were 5 major European conflicts involving these two powers.

  • 7 Years' War (1756-1763)
  • Napoleonic Wars (1813-1815)
  • Franco-Prussian War (1870-1871)
  • World War I (1914-1918)
  • World War II (1939-1945)

The longest period of peace during this time was 55 years between 1815 and 1870.

Major causes that lead to these, but also to other wars generally are (this list is not excessive):

  • Conflicts over natural resources
  • Nationalism
  • Opposing Group mentality
  • Autocratic leadership

How did the European Union mitigate these factors?

Conflicts over natural resources are fairly common in history. One factor in Franco-German relations was the natural resources of the Rhein-Ruhr area, which was used by Germany for military armament in World War I and World War II.

The origin of the EU lies in the European Coal and Steel Community, which lead to all member states gaining from trade in these commodities. From this grew a European free trade zone and later the European union. Bilateral trade generally leads to fewer violent conflicts between countries. There are many studies; some are here, here and here. Trade in the EU goes well beyond a simple free trade agreement.

Nationalism was a major factor in both world wars. This is also connected to the formation of opposing groups. The formation of groups leads to conflicts between these groups as a consequence of group polarization, even when the groups are formed arbitrarily. Before WWI Europe was divided between multiple allied groups (Germany-Austria, France-Britain).

The European Union basically replaced these opposing groups with one common European Group, which included the major former enemies, thereby giving the members a common goal. Furthermore it gives all member states a non-violent and regulated way to resolve conflicts and express interests between each other.

In WWI and before that most countries had autocratic leaders (Napoleon in France, Kaiser Wilhelm in Germany). Non-democratic countries have a higher probability to be involved in violent conflict than democratic countries. Furthermore, autocratic leaders before WWI were in a kind of battle for status among relatives, which they fought with military force.

The European Union encourages democratic countries. Membership in the European Union requires democratic elections, rules of law, etc. Tendencies towards autocracy in members states (as seen today in Poland) face opposition from the EU, which tries to keep members in a democratic discourse. Furthermore, countries who want to join the European Union have to adhere to the same standards, making violent conflicts with these states less likely.

Does this mean the EU caused peace?

No. Because this is not a natural science we have no control Europe to see if war had broken out without the European Union. But the EU and its predecessors established a system, whose elements generally reduce the risk of violent conflict. Additionally, a war between members of the European Union is not in sight at the moment and the period of piece of over 70 years is the longest in the last 250 years. With this information one could say that the European Union was one contributing factor to the period of piece since WWII.


The EU didn't prevent any wars. UK and France stopped going to war long before EU. So did Denmark and Sweden. The main reason there has been no wars between France and Germany after WW2 is that the Germans lost interest in wars after WW2 (France lost interest in wars after WW1, something that probably prolonged WW2 - if France hadn't been so reluctant to go to war again the phoney war could have been a real war and stopped German expansion early on. On the other hand, such a war might not had led to the same weariness of war in Germany as the real WW2 did. One can speculate for ever.).

This can of course not be proved but for anyone with common sense this is the most important explanation. WW2 made a clean house with German militarism. Ask any German school kid about what they study in history. This new German mentality and what is acceptable policy from a politician has nothing to do with EU and all to do with the embarrassment WW2 caused all new German generations since 1945.

Also compare to EFTA - no wars in between any of the (former) member states in EFTA. Western Europe was done with wars after WW2. Like Denmark and Sweden was done with rivalry after the Napoleonic wars after 800 years or so of hostilities and UK and France was done with their rivalry after the Fashoda incident.

  • What does it mean to say "France lost interest in wars"? They fought lengthy wars in Indochina in the 1940s and 50s and in Algeria in the 1950s, as well as participating in later military interventions in the Middle East and Africa.
    – Stuart F
    Oct 31, 2018 at 16:55
  • Those were small compared to the napoleonic wars or the Franco-Preussian war of 1870-1871. Besides, look how popular the responsible politicians for these colonial was become. Compare how France has behaved towards its neighbours and archenemies after WW1 with, e.g., how Russia behaves now. Russia (and USA) is clearly not done with wars in the way the great powers of Europa (excluding Russia) are.
    – d-b
    Oct 31, 2018 at 20:09

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