His main cult center was the Eshumesha temple in the Sumerian city-state of Nippur, where he was worshipped as the god of agriculture and the son of the chief-god Enlil. Though they may have originally been separate deities, in historical times, the god Ninĝirsu, who was worshipped in the Sumerian city-state of Girsu, was always identified as a local form of Ninurta. According to the Assyriologists Jeremy Black and Anthony Green, the two gods' personalities are "closely intertwined". As the city-state of Girsu declined in importance, Ninĝirsu became increasingly known as "Ninurta". He became primarily characterized by the aggressive, warlike aspect of his nature. In later times, Ninurta's reputation as a fierce warrior made him immensely popular among the Assyrians. In the late second millennium BC, Assyrian kings frequently held names which included the name of Ninurta, such as Tukulti-Ninurta ("the trusted one of Ninurta"), Ninurta-apal-Ekur ("Ninurta is the heir of [Ellil's temple] Ekur"), and Ninurta-tukulti-Ashur ("Ninurta is the god Aššur's trusted one"). Tukulti-Ninurta I (ruled 1243–1207 BC) declares in one inscription that he hunts "at the command of the god Ninurta, who loves me." Similarly, Adad-nirari II (ruled 911–891 BC) claimed Ninurta and Aššur as supporters of his reign, declaring his destruction of their enemies as moral justification for his right to rule. In the ninth century BC, when Ashurnasirpal II (ruled 883–859 BC) moved the capital of the Assyrian Empire to Kalhu, the first temple he built there was one dedicated to Ninurta. The walls of the temple were decorated with stone relief carvings, including one of Ninurta slaying the Anzû bird. Ashurnasirpal II's son Shalmaneser III (ruled 859–824 BC) completed Ninurta's ziggurat at Kalhu and dedicated a stone relief of himself to the god. On the carving, Shalmaneser III's boasts of his military exploits and credits all his victories to Ninurta, declaring that, without Ninurta's aid, none of them would have been possible. When Adad-nirari III (ruled 811–783 BC) dedicated a new endowment to the temple of Aššur in Assur, they were sealed with both the seal of Aššur and the seal of Ninurta. After the capital of Assyria was moved away from Kalhu, Ninurta's importance in the pantheon began to decline. Sargon II favored Nabu, the god of scribes, over Ninurta. Nonetheless, Ninurta still remained an important deity. Even after the kings of Assyria left Kalhu, the inhabitants of the former capital continued to venerate Ninurta,