in 706 BC and the year after, Sennacherib transferred the capital to Nineveh, which he ambitiously expanded and renovated. The 671 BC conquest of Egypt under Esarhaddon (681–669 BC) brought Assyria to its greatest ever extent. After the death of Ashurbanipal (669–631 BC), the Neo-Assyrian Empire swiftly collapsed. One of the primary reasons was the inability of the Neo-Assyrian kings to resolve the "Babylonian problem"; despite many attempts to appease Babylonia in the south, revolts were frequent all throughout the Sargonid period. The revolt of Babylon under Nabopolassar in 626 BC, in combination with an invasion by the Medes under Cyaxares in 615/614 BC, led to the Medo-Babylonian conquest of the Assyrian Empire. Assur was sacked in 614 BC and Nineveh fell in 612 BC. The last Assyrian ruler, Ashur-uballit II, tried to rally the Assyrian army at Harran in the west but he was defeated in 609 BC, marking the end of the ancient line of Assyrian kings and of Assyria as a state. Later history Despite the violent downfall of the Assyrian Empire, Assyrian culture continued to survive through the subsequent post-imperial period (609 BC – AD 240) and beyond. The Assyrian heartland experienced a dramatic decrease in the size and number of inhabited settlements during the rule of the Neo-Babylonian Empire founded by Nabopolassar; the former Assyrian capital cities Assur, Nimrud and Nineveh were nearly completely abandoned. Throughout the time of the Neo-Babylonian and later Achaemenid Empire, Assyria remained a marginal and sparsely populated region. Toward the end of the 6th century BC, the Assyrian dialect of the Akkadian language went extinct, having toward the end of the Neo-Assyrian Empire already largely been replaced by Aramaic as a vernacular language. Under the empires succeeding the Neo-Babylonians, from the late 6th century BC onward, Assyria began to experience a recovery. Under the Achaemenids, most of the territory was organized into the province Athura (Aθūrā). The organization into a single large province, the lack of interference of the Achaemenid rulers in local affairs, and the return of the cult statue of Ashur to Assur soon after the Achaemenids conquered Babylon facilitated the survival of Assyrian culture. Under the Seleucid Empire, which controlled Mesopotamia from the late 4th to mid-2nd century BC, Assyrian sites such as Assur, Nimrud and Nineveh were resettled and a large number of villages were rebuilt and expanded. After the Parthian Empire conquered the region in