The people migrated because they were always searching for food like fruit and vegetables, and they were always following game that they would hunt.
Well during the time of the hanging gardens, im pretty sure Nebuchadnezzar was in charge then. he created the hanging gardens for his wife to be in. his city was created with a surplus of food, a sytem of order and stability, troops, and jobs for everyone, baisicly meaning a market. the hanging gardens looked like a big white pyramid temple, with the inside of it hallow, just as if it was a skeleton for the pyramids. it had vines hanging down from the top, vines at the sides, almost like a veil to shield the outside from the inside. it had trees and birds, almost as if it was a miniature jungle, just without all the other animals. i truly hope this has helped you, and if u need anything else do tell me.
The best option would be "<span>Nations must acquire new territories and become world powers in order to survive," since this extending the individual idea of Darwinism to nation-states. </span>