Final answer:
The Neo-Sumerian Empire ended due to attacks from outside forces like the Elamites and Amorites, and possibly internal issues that weakened the empire's structure.
Step-by-step explanation:
The fall of the Neo-Sumerian Empire, also known as the Third Dynasty of Ur, was largely due to attacks from outside forces, specifically the Elamites and the Amorites. However, internal struggles and weak leadership potentially exacerbated the vulnerability of the Empire to these outside threats. Shu-Sin, a ruler of Ur, attempted to fend off the Amorite incursions by building a defensive wall, but this proved ineffective.
Eventually, the empire crumbled under the relentless assaults and sackings of its cities by invaders. Besides the external pressures, factors such as internal conflict and the lack of political leadership might have played roles in destabilizing the empire, making it an easier target for conquest.