"There is no king who is mighty by himself. Ten or 15 kings follow Hammurabi the ruler of Babylon, a like number of Rim-Sin of Larsa, a like number of Ibal-pi-el of Eshnunna, a like number of Amud-pi-el of Qatanum, but twenty follow Yarim-Lim of Yamhad." - A tablet sent to Zimri-Lim of Mari, describing Yarim-Lim I’s authority. 

Animal and plant domestication first began during the Neolithic Period around 12000 BCE in the swath of land known as the Fertile Crescent, which included all of Mesopotamia and then arched in northern Mesopotamia/Assyria, before covering most of the Levant, which is roughly equivalent with the modern nation-states of Israel, Palestine, Lebanon, and Syria. The process from nomadic hunter-gatherer societies to sedentary agriculture-based societies was gradual, though, and took place over a 2,000-year period. By about 8000 BCE, the first notable cities had formed, although they were more like towns by today’s standards in terms of size. Jericho in the Levant was one of the earliest notable towns, and by 6000 BCE, settlements had sprung up across the Fertile Crescent (Haywood 2005, 22). 

The creative impetus of organized society in the Fertile Crescent initially came from southern Mesopotamia, where the Sumerians introduced writing and other hallmarks of civilization to the region just before 3000 BCE, but in less than 1,000 years, things changed dramatically. Mesopotamia experienced the rise and fall of the Sumerian based dynasty in Uruk in the early third millennium BCE, followed by the Akkadian Dynasty in the mid-third millennium, and the Third Dynasty of Ur in the late third millennium. Each of these dynasties claimed hegemony over large parts of Mesopotamia during the apogees of their power, with the Ur III Dynasty even expanding its influence (but not control) into Syria and Persia. However, when these great regional powers collapsed, it created a vacuum in which new city-states would form, grow, and repeat the process. The city-states that were in the middle of Mesopotamia would either reap the benefits of this process by taking land and cities, or they would experience the pitfalls by being conquered or destroyed, but those on the periphery had a unique perspective and experience. 

As the Canaanites established themselves in most of the Levant and the Hurrians carved out space for themselves in northwestern Syria, a West Semitic ethnic group known as the Amorites entered Mesopotamia and Syria from the Arabian Desert. The movement of the Amorites and Hurrians coincided with the collapse of the Ur III Dynasty after 2004 BCE (Haywood 2005, 28), although it is not known for sure if the collapse of Ur III led to the movement of peoples, or if the movement at least partially led to the collapse. As the Ur III Dynasty grew weak internally, it could be that the Amorite attacks were a major factor in the destruction of the state. It must be stated, though, that it was the Elamites who ultimately delivered the coup de grace that brought Ur III to its knees. The more likely scenario is that the Amorites simply took advantage of the power vacuum that was created when Ur III collapsed. 

The Amorites actually belonged to several sub-tribes and did not necessarily move in unison, but they did migrate in such large numbers that they were able to overwhelm much of Mesopotamia and northeastern Syria by about 1800 BCE. All of the notable political dynasties and city-states from this period - Babylon, Mari, Assyria, Eshnunna, and Yamhad - were established by ethnic Amorites (Haywood 32-33), although only traces of the Amorite identity were retained.