Although the death of his father occurred far from home, Ashurbanipal assumed the kingship as planned. He may have owed his fortunes to the intercession of his grandmother Zakutu, who had recognized his superior capacities. He tells of his diversified education by the priests and his training in armour-making as well as in other military arts. He may have been the only king in Assyria with a scholarly background. As crown prince he also had studied the administration of the vast empire. The record notes that the gods granted him a record harvest during the first year of his reign. There were also good crops in subsequent years. During these first years he also was successful in foreign policy, and his relationship with his brother in Babylonia was good.

In 668 he put down a rebellion in Egypt and drove out King Taharqa, but in 664 the nephew of Taharqa, Tanutamon, gathered forces for a new rebellion. Ashurbanipal went to Egypt, pursuing the Ethiopian prince far into the south. His decisive victory moved Tyre and other parts of the empire to resume regular payments of tribute. Ashurbanipal installed Psamtik (Greek: Psammetichos) as prince over the Egyptian region of Sais. In 656 Psamtik dislodged the Assyrian garrisons with the aid of Carian and Ionian mercenaries, making Egypt again independent. Ashurbanipal did not attempt to reconquer it. A former ally of Assyria, Gyges of Lydia, had aided Psamtik in his rebellion. In return, Assyria did not help Gyges when he was attacked by the Cimmerians. Gyges lost his throne and his life. His son Ardys decided that the payment of tribute to Assyria was a lesser evil than conquest by the Cimmerians.

Graver difficulties loomed in southern Babylonia, which was attacked by Elam in 664. Another attack came in 653, whereupon Ashurbanipal sent a large army that decisively defeated the Elamites. Their king was killed, and some of the Elamite states were encouraged to secede. Elam was no longer strong enough to assume an active part on the international scene. This victory had serious consequences for Babylonia. Shamash-shum-ukin had grown weary of being patronized by his domineering brother. He formed a secret alliance in 656 with the Iranians, Elamites, Aramaeans, Arabs, and Egyptians, directed against Ashurbanipal. The withdrawal of defeated Elam from this alliance was probably the reason for a premature attack by Shamash-shum-ukin at the end of the year 652, without waiting for the promised assistance from Egypt. Ashurbanipal, taken by surprise, soon pulled his troops together. The Babylonian army was defeated, and Shamash-shum-ukin was surrounded in his fortified city of Babylon. His allies were not able to hold their own against the Assyrians. Reinforcements of Arabian camel troops also were defeated. The city of Babylon was under siege for three years. It fell in 648 amid scenes of horrible carnage, Shamash-shum-ukin dying in his burning palace.

After 648 the Assyrians made a few punitive attacks on the Arabs, breaking the forward thrust of the Arab tribes for a long time to come. The main objective of the Assyrians, however, was a final settlement of their relations with Elam. The refusal of Elam in 647 to extradite an Aramaean prince was used as pretext for a new attack that drove deep into its territory. The assault on the solidly fortified capital of Susa followed, probably in 646. The Assyrians destroyed the city, including its temples and palaces. Vast spoils were taken. As usual, the upper classes of the land were exiled to Assyria and other parts of the empire, and Elam became an Assyrian province. Assyria had now extended its domain to southwestern Iran. Cyrus I of Persia sent tribute and hostages to Nineveh, hoping perhaps to secure protection for his borders with Media. Little is known about the last years of Ashurbanipal’s reign.

Ashurbanipal left more inscriptions than any of his predecessors. His campaigns were not always recorded in chronological order but clustered in groups according to their purpose. The accounts were highly subjective. One of his most remarkable accomplishments was the founding of the great palace library in Nineveh (modern Kuyunjik), which is today one of the most important sources for the study of ancient Mesopotamia. The king himself supervised its construction. Important works were kept in more than one copy, some intended for the king’s personal use. The work of arranging and cataloging drew upon the experience of centuries in the management of collections in huge temple archives such as the one in Ashur. In his inscriptions Ashurbanipal tells of becoming an enthusiastic hunter of big game, acquiring a taste for it during a fight with marauding lions. In his palace at Nineveh the long rows of hunting scenes show what a masterful artist can accomplish in bas-relief; with these reliefs Assyrian art reached its peak. In the series depicting his wars, particularly the wars fought in Elam, the scenes are overloaded with human figures. Those portraying the battles with the Arabian camel troops are magnificent in execution.

One reason for the durability of the Assyrian empire was the practice of deporting large numbers of people from conquered areas and resettling others in their place. This kept many of the conquered nationalities from regaining their power. Equally important was the installation in conquered areas of a highly developed civil service under the leadership of trained officers. The highest ranking civil servant carried the title of tartān, a Hurrian word. The tartāns also represented the king during his absence. In descending rank were the palace overseer, the main cupbearer, the palace administrator, and the governor of Assyria. The generals often held high official positions, particularly in the provinces. The civil service numbered about 100,000, many of them former inhabitants of subjugated provinces. Prisoners became slaves but were later often freed.

No laws are known for the empire, although documents point to the existence of rules and standards for justice. Those who broke contracts were subject to severe penalties, even in cases of minor importance: the sacrifice of a son or the eating of a pound of wool and drinking of a great deal of water afterward, which led to a painful death. The position of women was inferior, except for the queen and some priestesses.

As yet there are no detailed studies of the economic situation during this period. The landed nobility still played an important role, in conjunction with the merchants in the cities. The large increase in the supply of precious metals—received as tribute or taken as spoils—did not disrupt economic stability in many regions. Stimulated by the patronage of the kings and the great temples, the arts and crafts flourished during this period. The policy of resettling Aramaeans and other conquered peoples in Assyria brought many talented artists and artisans into Assyrian cities, where they introduced new styles and techniques. High-ranking provincial civil servants, who were often very powerful, saw to it that the provincial capitals also benefited from this economic and cultural growth.

Harran became the most important city in the western part of the empire; in the neighbouring settlement of Huzirina (modern Sultantepe, in northern Syria), the remains of an important library have been discovered. Very few Aramaic texts from this period have been found; the climate of Mesopotamia is not conducive to the preservation of the papyrus and parchment on which these texts were written. There is no evidence that a literary tradition existed in any of the other languages spoken within the borders of the Assyrian empire at this time, except in peripheral areas of Syria and Palestine.

Culturally and economically, Babylonia lagged behind Assyria in this period. The wars with Assyria—particularly the catastrophic defeats of 689 and 648—together with many smaller tribal wars disrupted trade and agricultural production. The great Babylonian temples fared best during this period, since they continued to enjoy the patronage of the Assyrian monarchs. Only a few documents from the temples have been preserved, however. There is evidence that the scribal schools continued to operate, and “Sumerian” inscriptions were even composed for Shamash-shum-ukin. In comparison with the Assyrian developments, the pictorial arts were neglected, and Babylonian artists may have found work in Assyria.

During this period people began to use the names of ancestors as a kind of family name; this increase in family consciousness is probably an indication that the number of old families was growing smaller. By this time the process of “Aramaicization” had reached even the oldest cities of Babylonia and Assyria.

Apparently this era was not very fruitful for literature either in Babylonia or in Assyria. In Assyria numerous royal inscriptions, some as long as 1,300 lines, were among the most important texts; some of them were diverse in content and well composed. Most of the hymns and prayers were written in the traditional style. Many oracles, often of unusual content, were proclaimed in the Assyrian dialect, most often by the priestesses of the goddess Ishtar of Arbela. In Assyria as in Babylonia, the beginnings of a real historical literature are observed; most of the authors have remained anonymous up to the present.

The many gods of the tradition were worshiped in Babylonia and Assyria in large and small temples, as in earlier times. Very detailed rituals regulated the sacrifices, and the interpretations of the ritual performances in the cultic commentaries were rather different and sometimes very strange.

On some of the temple towers (ziggurats), astronomical observatories were installed. The earliest of these may have been the observatory of the Ninurta temple at Kalakh in Assyria, which dates back to the 9th century bc; it was destroyed with the city in 612. The most important observatory in Babylonia from about 580 was situated on the ziggurat Etemenanki, a temple of Marduk in Babylon. In Assyria the observation of the Sun, Moon, and stars had already reached a rather high level; the periodic recurrence of eclipses was established. After 600, astronomical observation and calculations developed steadily, and they reached their high point after 500, when Babylonian and Greek astronomers began their fruitful collaboration. Incomplete astronomical diaries, beginning in 652 and covering some 600 years, have been preserved.