War and Peace Systems

Many societies go to war but many societies have also been known to maintain peace systems for generations. What is it that they’re doing different? Examples of such peace systems are Nordic Nations, who have not warred among each other for 200 years. There were many instances where wars could have been fought but weren’t - such as when Norway gained independence from Sweden in 1905, which was done so peacefully or when there was a dispute between Finland and Sweden over the Åland Islands. This study is looking to identify certain features that exist in such peace systems. What is it that they do different, that the rest of the societies can learn from?