There were many changes in power in Mesopotamia over thousands of years as different empires rose and fell. The Hittites were the first to use iron weapons around 1600-900 BC but lost their advantage when iron technology spread. The Assyrians built a powerful militaristic empire from 850-612 BC conquering Egypt, Palestine and Mesopotamia under King Ashurbanipal and constructing a massive capital and library at Nineveh. The Chaldeans or "New Babylonians" then ruled from 612-550 BC under King Nebuchadnezzar, establishing the new capital of Babylon and building the Hanging Gardens. Finally, Cyrus the Great's Persian Empire arose from 550-