The Neo-Babylonian Empire was a period of Mesopotamian history which began in 626 BC and ended in 539 BC. During the preceding three centuries, Babylonia had been ruled by their fellow Akkadian speakers and northern neighbours, Assyria. A year after the death of the last strong Assyrian ruler, Assurbanipal, in 627 BC, the Assyrian empire spiralled into a series of brutal civil wars. Babylonia rebelled under Nabopolassar, a member of the Chaldean tribe which had migrated from the Levant to south eastern Babylonia in the early 9th century BC. In alliance with the Medes, Persians, Scythians and Cimmerians, they sacked the city of Nineveh in 612 BC, and the seat of empire was transferred to Babylonia for the first time since the death of Hammurabi in the mid 18th century BC. This period witnessed a general improvement in economic life and agricultural production, and a great flourishing of architectural projects, the arts and science.