If I were to give a very general answer, this is the concept of imperialism/expansionism. Humans seek to improve themselves by nature i.e. rich people want to become richer. In the same way, Japan (and actually any powerful country) would want to expand and colonise/seize other countries to improve their global standing and become more powerful. (Imagine if Japan seized every country - we would be under their control! - just a thought haha)
Crops grain and fabrics are the answers
<span>check the executive and judicial branches</span>
If I could do research on any type of collective behavior it would be mass hysteria. Mass hysteria is the result of fears and rumors being illusion-ed or real. This is created through society and populations. I would study mass hysteria because of the interesting people and stories of those people you can learn about and how they view the world as a individual person.