I can't understand the reason behind nationalism: it increases hassle and hate between populations. This feeling of belonging to a certain land, category, religion, or politics leads people to fight against each other. Trust me, there's no noble cause behind the war. We should all defend humanity, knowing that nothing else is more important than living all together in peace instead of losing thousands if not millions of people for a piece of land.
So why do we have to be so selfish to the point we accept killing and terrorizing others seeking better conditions because our lands are getting bigger and bigger.
Personally, I don't have a lot of hope that war is going to stop one day, I do appreciate the efforts of the organizations that try to spread love and peace all around the world but I think it's an impossible task, maybe things are going slightly to improve but the war won't stop because there's always a reason for governments to start it.
Power is a common thing that every country's leader wants to possess and the only way is to get more sources of metal, phosphate, water, gold/diamonds so if your country has one of those things or maybe something else valuable, you should consider that there's a very big chance to your land to be vanished especially if you have not a strong military service.