Pax Europaea

Pax Europaea (English: the European peace – from the historic Pax Romana), is the period of relative peace experienced by Europe in the period following World War II—often associated above all with the creation of the European Union (EU) and its predecessors.Cold War this peace was even more evident because of the fall of political tensions, with the major exception of most of the former Yugoslavia.

 After the
Transatlantic cooperation and European integration was designed to maintain the fragile peace that was created in Europe. With the continent consistently falling into war over the past centuries the creation of the European Communities in the 1950s set to integrate its members to such an extent that war between them would be impossible. 

These Communities, and other organisations including NATO expanded to cover most of Western Europe, Northern Europe and Southern Europe. Although Central and Eastern Europe remained under Soviet influence, they too experienced little conflict, with the exception of internal repression, until the 1990s when a series of wars in Yugoslavia broke out as the country disintegrated. The EU structures were criticised for its inability to prevent the conflict, though the zone is now within its sphere of enlargement.

The EU now comprises 28 countries with majority of European non-member states seeking membership (twelve countries joined the EU in 2000s). In addition to that, most countries which remain outside are tied to the EU by economic agreements and treaties such as the European Economic Area. Within the zone of integration, there has been no conflict since 1945, making it the longest period of peace on the western European mainland since Pax Romana.

The European Union was awarded the 2012 Nobel Peace Prize in recognition of its efforts to maintain and actively foster peace within its borders as well as internationally through diplomatic means.
However, there were many wars in Europe during that time, and European countries remained warlike, especially with regard to former colonies.

Reference: http://en.wikipedia.org/wiki/File:Enlargement_of_the_European_Union_77.gif