The last one, It began when Cyrus the Great united nomadic herding tribes. and here is why,
The Persian Empire began as a collection of semi-nomadic tribes as it raised sheeps, goats and cattle, founded the first Persian Empire which was also known as Achaemenid Empire, in 550 B.C. The first one was under Cyrus the Great and it soon became the world's first superpower
the Chinese wanted North Korea as a Communist buffer state to protect their northeastern provinces that made up Manchuria and they also felt threatened by the American fleet that lay off their coast.
