During the Neo-Assyrian and Neo-Babylonian Empires, Arameans, the native speakers of Aramaic, began to settle in greater numbers, at first in Babylonia, and later in Assyria (Upper Mesopotamia, modern-day northern Iraq, northeast Syria, northwest Iran, and south eastern Turkey (what was Armenia at the time). The influx eventually resulted in the Neo-Assyrian Empire (911–605 BC) adopting an Akkadian-influenced Imperial Aramaic as the "lingua franca" of its empire. This policy was continued by the short-lived Neo-Babylonian Empire and Medes, and all three empires became operationally bilingual in written sources, with Aramaic used alongside Akkadian. The Achaemenid Empire (539–323 BC) continued this tradition, and the extensive influence of these empires led to Aramaic gradually becoming the lingua franca of most of western Asia, the Arabian Peninsula, Anatolia, the Caucasus, and Egypt.