Eanatum was the son of Akurgal, and the most militarily successful ruler of the first dynasty of Lagash. He conducted many campaigns abroad, including ones against the southern cities of Ur, Uruk, and Kiutu, as well as states further afield such as Kish, Mari, Akshak, and Susa. He even reached northeastern Subartu and the eastern regions of Elam, destroying a city called Mishime. His military campaigns were so widespread that he was able to claim the title "King of Kish", a title associated with if not always actually indicating, the unity of the Mesopotamian city-states and their submission to a single ruler.

Like other Lagash rulers, Eanatum had to deal with Umma and the unsettled struggle over the Guedena. From the Enmetena cone we know he was in a strong position to dictate terms of an agreement. He divided the land with his rival Enakale and established a no-man's land along the agreed border, marking it with his own boundary stele and restoring the previously ruined stele of Mesalim, in addition to building shrines to Enlil, Ningirsu, and Ninhursag near the division. He also imposed a tax on Umma for the use of its share of the Guedena, which grew to huge proportions and in the time of his descendants resulted in another invasion by Umma into Lagash's side. To enforce the agreement he made the ruler of Umma swear an oath to the gods not to violate the borders.

Much information about Eanatum's deeds comes from the famous Stele of the Vultures (FAOS 05/1, Ean 01), a now fragmentary inscription that depicts in both verbally and graphically powerful ways the military exploits of the king of Lagash. One fragment shows the god Ningirsu holding a mace in his right hand while his left holds a net that has bagged a number of helpless enemy soldiers. Another section shows Eanatum leading a heavily armed phalanx of soldiers trampling slain enemy underneath. Yet another shows men piling up corpses into a giant heap, an image which is reflected in the text.

The stele also gives testament to developments in the ideology of kingship which are promoted by later Lagash rulers. Eanatum is the first Lagash king to explicitly claim divine birth by a god, in this case Ningirsu. Inheritors of the throne would go on to do likewise, as when Eanatum's son Enanatum I named the god Lugal-URU11 his father, and when Enmetena names Gatumdug his divine mother (Bauer pg. 462). Along with the divine progenitor comes a divine wet-nurse, that is, a female goddess who suckles the king to make him strong. For Eanatum this figure is the ancient goddess Ninhursag (Ean 01, IV). Other kings, down to the Neo-Assyrian period, would also make use of this motif. The stele also describes how Ningirsu visited Eanatum in a dream where he instructed him to make war on Umma. This motif surfaces again in the cylinder inscriptions of the later king Gudea, where he narrates how Ningirsu explained the plan for the (re)building of his E-ninnu temple.