Mesopotamia: Crash Course World History #3

They also knew how to write, ability which was initially used for record keeping: X gave Y three bushels of wheat and Y gave Z two goats.

But they also had slaves and a class system and, as not everyone could read and write, this ability further widended the gap between classes.

The land of Mesopotamia was fertile, but it lacked in other materials, such as wood or stone. Thus, the people from Mesopotamia started trading, creating the first territorial kingdom. 

In around 2000 BCE, Mesopotamia probably started to suffer from severe draughts (because of the shifting river courses) and the Mesopotamian cities were conquered by pastoral nomads.

Along with the nomads, a new system was put in place, similar to today's private enterpise system. This led to the introduction of taxes.

The tribal leaders became kings, who wanted to expand their power outwards and also pass it down to their sons.

Hammurabi lead the kingdom between 1792 BCE and 1750 BCE, creating the now famous Code of Hammurabi, full of laws and a moral code.

The Assyrians were no longer a kingdom, but an empire, streching as far as Egypt.

The army was a meritocracy, generals being awarded on merit, not on bloodline.

Their actions and conquests were motivated by the need to satisfy Ashur, the great god of the neo-Assyrians.