His reign was marked by the violent uprisings of areas conquered by his father and the abandonment of several important cities (primarily in Sumer).

Samsu-iluna seems to have taken a defensive approach after this; in the 18th year of his reign, he saw to the rebuilding of 6 fortresses in the vicinity of Nippur[6]: 380–382  which might have been intended to keep that city under Babylonian control.

[2]: 243  In Assyria, a native vice regent named Puzur-Sin ejected Asinum who had been a vassal king of his fellow Amorite Hammurabi.

Samsu-Iluna seems to have been powerless to intervene, and finally a king named Adasi, restored a stable native dynasty in Assyria, removing any vestages of Amorite-Babylonian influence[7]: section 576 apud [2]: 243 In the end, Samsu-iluna was left with a kingdom that was only fractionally larger than the one his father had started out with 50 years prior (but which did leave him mastery of the Euphrates up to and including the ruins of Mari and its dependencies).

[4]: 115 [Note 4] The status of Eshnunna is difficult to determine with any accuracy, and while it may have remained in Babylonian hands the city was exhausted and its political influence at an end.

Samsu-iluna's campaigns might not have been solely responsible for the havoc wreaked upon Uruk and Ur, and his loss of Sumer might have been as much a calculated retreat as defeat.

These breaks are also observed in the archeological record, where evidence points to these cities being largely or completely abandoned for hundreds of years, until well into the Kassite period.

Certainly the constant warfare cannot have helped matters, but Samsu-iluna appears to have campaigned just as hard in the north, and that region was thriving during the period.

[1]: 49–50  It is also possible that economic or environmental factors were involved; it is known that both Hammurabi and Rim-sin I had instituted policies which altered the economies of the region,[4]: 115  perhaps these proved unsustainable in the long-term.