In bringing about his sudden social revolution, Urukagina had at the same time unwittingly let loose the forces of disorder.  Discontented and unemployed officials, and many representatives of the despoiled leisured and military classes of Lagash, no doubt sought refuge elsewhere, and fostered the spirit of revolt which ever smouldered in subject states.  At any rate, Umma, remembering the oppressions of other days, was not slow to recognize that the iron hand of Lagash had become unnerved.  The zealous and iconoclastic reformer had reigned but seven years when he was called upon to defend his people against the invader.  He appears to have been utterly unprepared to do so.  The victorious forces of Umma swept against the stately city of Lagash and shattered its power in a single day.  Echoes of the great disaster which ensued rise from a pious tablet inscription left by a priest, who was convinced that the conquerors would be called to account for the sins they had committed against the great god Nin-Girsu.  He lamented the butchery and robbery which had taken place.  We gather from his composition that blood was shed by the raiders of Umma even in the sacred precincts of temples, that statues were shattered, that silver and precious stones were carried away, that granaries were plundered and standing crops destroyed, and that many buildings were set on fire.  Amidst these horrors of savagery and vengeance, the now tragic figure of the great reformer suddenly vanishes from before our eyes.  Perhaps he perished in a burning temple; perhaps he found a nameless grave with the thousands of his subjects whose bodies had lain scattered about the blood-stained streets.  With Urukagina the glory of Lagash departed.  Although the city was rebuilt in time, and was even made more stately than before, it never again became the metropolis of Sumeria.

The vengeful destroyer of Lagash was Lugal-zaggisi, Patesi of Umma, a masterful figure in early Sumerian history.  We gather from the tablet of the unknown scribe, who regarded him as a sinner against the god Nin-Girsu, that his city goddess was named Nidaba.  He appears also to have been a worshipper of Enlil of Nippur, to whose influence he credited his military successes.  But Enlil was not his highest god, he was the interceder who carried the prayers of Lugal-zaggisi to the beloved father, Anu, god of the sky.  No doubt Nin-Girsu represented a school of theology which was associated with unpleasant memories in Umma.  The sacking and burning of the temples of Lagash suggests as much.

Having broken the power of Lagash, Lugal-zaggisi directed his attention to the rival city of Kish, where Semitic influence was predominating.  When Nanizak, the last monarch of the line of the famous Queen Azag-Bau, had sat upon the throne for but three years, he perished by the sword of the Umma conqueror.  Nippur likewise came under his sway, and he also subdued the southern cities.