Šamaš-šuma-ukin ( or , meaning "Shamash has established the name"), was king of Babylon as a vassal of the Neo-Assyrian Empire from 668 BC to his death in 648. Born into the Assyrian royal family, Šamaš-šuma-ukin was the son of the Neo-Assyrian king Esarhaddon and the elder brother of Esarhaddon's successor Ashurbanipal.
Despite being the elder son, Šamaš-šuma-ukin was for unknown reasons bypassed as heir to Assyria. His designation as heir to Babylonia was likely devised by Esarhaddon as a means to counteract future rivalry and jealousy between the brothers. Although Esarhaddon specified that Šamaš-šuma-ukin was to swear an oath of allegiance to Ashurbanipal, the clear primary heir, Šamaš-šuma-ukin was also referred to as Ashurbanipal's "equal brother" and Ashurbanipal was to stay out of his affairs. This part of the succession plans were not upheld by Ashurbanipal after Esarhaddon's death; Šamaš-šuma-ukin only acceded to the Babylonian throne months after Ashurbanipal had become king and was throughout his reign a closely monitored vassal, not entrusted with all of Babylonia or substantial military forces and only allowed to make decisions if they were approved and verified by Ashurbanipal.
Šamaš-šuma-ukin assimilated well into Babylonia, despite being ethnically and culturally Assyrian. His royal inscriptions are far more "quintessentially Babylonian" than those of other Assyrian rulers of southern Mesopotamia, using Babylonian imagery and rhetoric to an unprecedented extent. He participated in the Babylonian New Year's festival and is recorded as partaking in other Babylonian traditions. The Statue of Marduk, the main cult image of Babylon's patron deity Marduk, was returned to Babylon in 668 at Šamaš-šuma-ukin's coronation, having been stolen from the city by his grandfather Sennacherib twenty years prior.
Though Šamaš-šuma-ukin maintained peaceful relations with his younger brother for many years, resentment gradually grew between them due to Ashurbanipal's overbearing control. In 652, Šamaš-šuma-ukin revolted, inspiring the Babylonians to join him and recruiting a coalition of enemies of Assyria, including the Elamites, Chaldeans, Arameans and perhaps the Medes. Though the conflict was initially indecisive, it eventually ended in disaster for Šamaš-šuma-ukin. Babylon was captured by Ashurbanipal in 648 after a lengthy siege and Šamaš-šuma-ukin died, though the exact circumstances of his death are unclear. After his defeat and death there is evidence of a large-scale damnatio memoriae campaign, with images of the king being mutilated, erasing his face.
Background
Šamaš-šuma-ukin was probably the second eldest son of Esarhaddon, the third king of the Sargonid dynasty, younger only than the crown prince Sin-nadin-apli. Upon the unexpected death of Sin-nadin-apli in 674 BC, the Assyrian court was thrown into upheaval. Esarhaddon had only become king through great difficulty and wished to avoid his own eventual death initiating a succession crisis. He thus soon began to draw up new succession plans. Esarhaddon decided that the fourth-eldest son Ashurbanipal would inherit Assyria, clearly the primary title. Šamaš-šuma-ukin, the next-eldest son after Sin-nadin-apli, was instead designated as the heir to Babylonia, with the two designated as "equal brothers". The third eldest son Šamaš-metu-uballiṭ was entirely bypassed, perhaps because he suffered from poor health. Despite proclaiming his two sons as equals, Esarhaddon also made it clear that Šamaš-šuma-ukin was to swear an oath of allegiance to Ashurbanipal.
After Esarhaddon made his decision, the two princes arrived at the Assyrian capital of Nineveh together and partook in a celebration in May 672 with foreign representatives, Assyrian nobles and elements of the military. Promoting one son as heir to Assyria and the other as heir to Babylonia was a novel idea; for the past decades the Assyrian king had simultaneously ruled Babylonia. The decision to bypass Šamaš-šuma-ukin as heir to Assyria was also a remarkable one, given that Esarhaddon's own accession issues had been the direct result of his father Sennacherib acting in a similar way. Sennacherib had bypassed the elder son Arda-Mulissu in favor of the younger Esarhaddon; in Sennacherib's case this decision led to Arda-Mulissu murdering him and fighting a civil war against Esarhaddon. Why Esarhaddon made nearly the same decision is not clear.
One hypothesis in regard to why a younger son was designated as the heir to what was clearly Esarhaddon's primary title is that Ashurbanipal and Šamaš-šuma-ukin could have had different mothers. Though it is equally likely that Šamaš-šuma-ukin and Ashurbanipal shared a mother, possibly Ešarra-ḫammat (Esarhaddon's primary consort), it is also possible that Ashurbanipal was the son of an Assyrian woman and Šamaš-šuma-ukin was the son of a Babylonian woman; Šamaš-šuma-ukin acceding to the Assyrian throne could thus have been problematic. The decision to grant Šamaš-šuma-ukin Babylonia and designate him and Ashurbanipal as "equal brothers" could perhaps be due to Esarhaddon wishing to avoid the rivalry and jealousy involved in his own accession. If Šamaš-šuma-ukin had Babylonian heritage, Esarhaddon could have surmised that he was a superior candidate for the Babylonian throne.
As crown prince, Šamaš-šuma-ukin would have undergone training for traditional royal duties, such as hunting, riding, scholarship and wisdom, archery, chariotry and other forms of military training. Because Esarhaddon was constantly ill, much of the administrative duties of the empire fell upon Ashurbanipal and Šamaš-šuma-ukin during the last few years of their father's reign. It was important for the crown princes to gain real experience in ruling. Letters of correspondence between Esarhaddon and Ashurbanipal from this time for instance show that Ashurbanipal prominently participated in the Assyrian intelligence network, gathering information on foreign enemies and rivals and compiling reports for his father.
Ashurbanipal immediately became king of Assyria upon Esarhaddon's death. Šamaš-šuma-ukin was somewhat belatedly crowned as king of Babylon in the spring of the next year. His coronation was marked by Ashurbanipal returning the religiously important Statue of Marduk, stolen by Sennacherib twenty years prior, to Babylon. The return of the statue was particularly important as it in the eyes of the Babylonians cemented the approval of Marduk, the Babylonian national deity, of the new king's rule. Though Šamaš-šuma-ukin, an Assyrian prince, being installed as the king of Babylon was in a way an embodiment of Assyrian hegemony, his coronation ceremony (parallelling that of Ashurbanipal) and the return of the Statue of Marduk were efforts made to portray him as an independent king of Babylon. Šamaš-šuma-ukin would rule at Babylon for sixteen years, apparently mostly peacefully in regard to his younger brother, but there would be repeated disagreements on the exact extent of his control; despite the requirement of an oath of allegiance to Ashurbanipal, Esarhaddon had also specified that Ashurbanipal was not to interfere in Šamaš-šuma-ukin's affairs. This part of the succession plans were not upheld by Ashurbanipal, who perhaps shifted the balance of power in his own favor and diminished Šamaš-šuma-ukin's intended status out of fear that his elder brother given a strong power-base would threaten his rule.
Reign
Early reign and status
Šamaš-šuma-ukin was the only member of the Assyrian royal family to accede to the Babylonian throne and intentionally never to the Assyrian one. The only other Assyrian prince who ruled Babylon and not Assyria was Šamaš-šuma-ukin's uncle Ashur-nadin-shumi, though he had been the crown prince of Sennacherib and the intended successor in Assyria as well. Though Ashurbanipal, as king of Assyria, was more powerful, Šamaš-šuma-ukin's kingship of Babylon, important to the Assyrians for military, political, religious and ideological reasons, was prestigious in its own right. He was however very clearly a closely monitored vassal rather than an autonomous ruler. Though Esarhaddon's inscriptions suggest that Šamaš-šuma-ukin should have been granted the entirety of Babylonia to rule, contemporary records only definitely prove that Šamaš-šuma-ukin held Babylon itself and its vicinity. The governors of some Babylonian cities, such as Nippur, Uruk and Ur, and the rulers in the Sea Land, all ignored the existence of a king in Babylon and saw Ashurbanipal as their monarch. Šamaš-šuma-ukin was also not entrusted with any substantial military forces; when the Elamite king Teumman invaded Babylonia in 653, Šamaš-šuma-ukin was unable to defend his country and had to rely on Ashurbanipal for military support.
Šamaš-šuma-ukin is recorded as having participated in several traditional Babylonian royal activities. He rebuilt the walls of the city Sippar and is known to have participated in the Babylonian New Year's festival, which had been suspended during the time that the god's statue was absent from the city. He gave considerable attention to the temples of his domain, confirming offerings in several temples in his inscriptions and increasing the land of the Ishtar temple in Uruk. Šamaš-šuma-ukin was ethnically and culturally Assyrian, but appears to have assimilated well into Babylonia. His royal inscriptions are far more "quintessentially Babylonian" than those of other Assyrian rulers of southern Mesopotamia, using Babylonian imagery and rhetoric to an unprecedented extent, almost as if overriding his actual cultural and ethnic origin as an Assyrian. Though he was in Assyria at some points, such on one occasion when he was feeling sick, Šamaš-šuma-ukin was presumably the first of his dynasty to live in Babylon full-time. Throughout his reign, Šamaš-šuma-ukin partook in several building projects, an important aspect of Babylonian kingship to the same degree as military campaigns were important in Assyrian kingship. He is recorded as restoring shrines in several cities and as rebuilding the city wall of Sippar.
Despite his kingship having been designated by Esarhaddon, Ashurbanipal refers to himself in his inscriptions as the man who granted Šamaš-šuma-ukin rule over Babylon. This is possibly due to Šamaš-šuma-ukin only being formally crowned as king a few months after Ashurbanipal had become the Assyrian monarch. It would also theoretically have been within Ashurbanipal's power to stop Šamaš-šuma-ukin's coronation.
Worsening relations
The exact reasons for Šamaš-šuma-ukin's revolt against Ashurbanipal are unknown, but there are several possibilities. Perhaps the most commonly believed reason is that although Esarhaddon had designated Šamaš-šuma-ukin to inherit control of all of Babylonia, this had not been respected by Ashurbanipal once Esarhaddon was dead. Although business documents from Šamaš-šuma-ukin are known throughout Babylonia (suggesting that most of the region saw him as their king), similar documents dated to the reign of Ashurbanipal are also known from Babylonia, which suggests that Ashurbanipal had assumed the authority of a Babylonian monarch despite there already being a king in Babylon.