When a nation entering the state of war, most people would view another person is the extension of themselves in the same nation, view the successful killing as the winning of themselves. If someone says: "It's all about the military industrial complex, they are the true winners!"People would just attack this person.

I think that's the same thing with people becoming super possessive and even violent over sports teams. I never understood it for the longest time - how can you become so wound up over them winning or losing if you had nothing to do with it? I would understand if you bet money on that team or something. But like this? I think it's the same thing as you said above, associating themselves with some team to be able to feel good about the achievements of others? Something like that, at least.