The title simultaneously laid a claim on the legacy and glory of the ancient empire that had been founded by Sargon of Akkad (r. 2334–2279 BC) and expressed a claim to rule the entirety of lower Mesopotamia (composed of the regions of Sumer in the south and Akkad in the north).
Though his empire stretched far and wide, one of its most important regions was Sumer, the southern parts of lower Mesopotamia, where city states had competed with each other for universal rule for centuries.
[5] The political union of Sumer and Akkad under the Akkadian Empire, the largest empire that the world had yet seen, was seen as a monumentous event even in contemporary times, with both Sargon and Naram-Sin soon becoming legendary figures who would frequently appear in later Mesopotamian discussions on history.
[6] During the reign of Naram-Sin's son Shar-Kali-Sharri (r. c. 2217–2193 BC) the Akkadian Empire began to collapse as a result of widespread drought and an invasion by the nomadic Gutians.
[7][8]'In the 2100s BC, the Gutians destroyed the city of Akkad and supplanted the ruling Sargonic dynasty with their own line of kings of Sumer.
[10] After the collapse of the Dynasty of Isin, the king Rim-Sin of Larsa (r. c. 1758–1699 BC) claimed its legacy but he was soon defeated by Hammurabi of Babylon (r. c. 1728–1686 BC) who conquered the considerable kingdom that Rim-Sin ruled (which included prominent cities like Uruk and the previous capital Isin).
[14] Through either outright conquest or forcing other states to pay tribute, Hammurabi extended Babylonian rule throughout Mesopotamia and while his early reign may be characterizable as a dual monarchy of sorts, ruling both Sumer and Akkad as more or less separate entities, his conquests to the northeast and north saw the formation of a true empire, which would not stay intact under his successors.
After Tiglath-Pileser III's reign, Babylon rebelled again and his son Sargon II (r. c. 722–705 BC) was also forced to reconquer it once more, only using the title upon his victory.
[16] To the Assyrians, the title was not only a claim to the prestige and legacy of Sargon of Akkad and the Akkadian Empire but also a formal assertion of sovereignty over Babylon.
[22] The title of "King of Lands", also used by Assyrian monarchs since at least Shalmaneser III (r. c. 859–824 BC),[23] was also adopted by Cyrus the Great and his successors.
[13] Kings of Sumer and Akkad in the Neo-Babylonian Empire: After regaining independence, the rulers of Babylon continued to use the title.