The final ruler to claim the title was the first Persian Achaemenid king, Cyrus the Great, after his conquest of Babylon in 539 BC.
The term "four corners of the world" appears in several ancient mythologies and cosmologies, wherein it roughly corresponds the four points of the compass.
[11] The term thus covers a somewhat clear geographical region, corresponding to Mesopotamia and its surroundings, but should be understood as referring to the entire known world.
At the point in time when the title was first used, the 2200s BC, the Mesopotamians would have equated all of Mesopotamia to the entire world; the region was highly productive, densely populated and was bordered on all sides by seemingly empty and uninhabited lands.
[13] During the Early Dynastic Period in Mesopotamia (c. 2900–2350 BC), the rulers of the various city-states in the region would often launch invasions into regions and cities far from their own, at most times with negligible consequences for themselves, in order to establish temporary and small empires to either gain of keep a superior position relative to the other city-states.
[12] Rulers attempting to reach a position of universal rule became more common during the Early Dynastic IIIb period (c. 2450–2350 BC) during which two prominent examples are attested.
[15] The first, Lugalannemundu, king of Adab, is claimed by the Sumerian King List (though this is a much later inscription, making the extensive rule of Lugalennemundu somewhat doubtful) to have created a great empire covering the entirety of Mesopotamia, reaching from modern Syria to Iran, saying that he "subjugated the Four Corners".
[1] Sargon, king of Akkad, unified Lower and Upper Mesopotamia, creating the first true Mesopotamian empire.
[2][6] Naram-Sin also proclaimed himself to be a living god (the first Mesopotamian king to do so), making his capital of Akkad not only the political but also the religious center of the empire.
[6][23] Some ancient sources confer the title onto Ur-Nammu as well, referring to him as "King in Heaven and the Four Corners of the World", but these inscriptions date to centuries after his reign.
[29] Sargon II's son and heir Sennacherib (r. 705–681 BC) did not immediately inherit the title, referring to himself simply as the "unrivaled king" at the beginning of his reign.
British historian Stephanie Dalley, specializing in the Ancient Near East proposed in 1998 that the title may have had to be earned through the king successfully campaigning in all four points of the compass.
Dalley also proposed that the similar title of "King of the Universe", with a virtually identical meaning, would have been earned through seven (which would have been connected to totality in the eyes of the Assyrians) successful campaigns.
Unlike previous ruling dynasties in Mesopotamia, the Neo-Babylonians usually only employed one royal title on any one occasion.
[38] The title of "King of Lands", also used by Assyrian monarchs since at least Shalmaneser III,[39] was also adopted by Cyrus the Great and his successors.