If people have decent jobs and prospects they usually don't want to go to war.
If there is a huge economic collapse and millions end up unemployed they will start looking for someone to blame.
When empires collapse people from the former colonies start migrating towards the centre of the imperial power because they perceive that is where the wealth and power is.
This is what seems to be happening today.
Millions from former colonies in Africa, the Middle East and Asia all want to get to Europe.
The German government has just passed legislation to allow more migrants from outside the EU to enter Germany.
They claim that there are 1 million unfilled job vacancies in Germany which they can't fill even with Labour imports from Eastern Europe, the German nation has the same problem as the rest of Europe, demographically they are committing suicide because they have an aging population and not enough younger workers to replace them.
Britain has the same problem, to many oldies and not enough younger people coming into the workforce to pay N.I. and taxes to support them, this means either produce more indigenous workers through larger families or take the easy option of importing ready make workers through mass immigration.
Absolutely spot on. Wonder if that's why France considered giving mothers 1,000 euros a month for having extra children. I'm personally of the view that there are too many people on Earth but it's dangerous for Europe when artificial population increase is totally outstripping natural birth rates.