The Medes were an ancient Iranian people. They had established their own empire by the 6th century BC, having defeated the Neo-Assyrian Empire with the Chaldeans. They overthrew Urartu later on as well. The Medes are credited with the foundation of the first Iranian empire, the largest of its day until Cyrus the Great established a unified Iranian empire of the Medes and Persian, often referred to as the Achaemenid Empire, by defeating his grandfather and overlord, Astyages the king of Media.The Achaemenid Empire was the largest and most significant of the Persian Empires, and followed the Median Empire as the second great empire of the Iranians. It is noted in western history as the foe of the Greek city states in the Greco-Persian Wars, for freeing the Israelites from their Babylonian captivity, for its successful model of a centralized bureaucratic administration, the Mausoleum of Halicarnassus (one of the Seven Wonders of the Ancient World), and for instituting Aramaic as the empire's official language. Because of the Empire's vast extent and long endurance, Persian influence upon the language, religion, architecture, philosophy, law and government of nations around the world lasts to this day. At the height of its power, the Achaemenid dynasty encompassed approximately 8.0 million square kilometers, held the greatest percentage of world population to date, stretched three continents (Europe, Asia and Africa) and was territorially the largest empire of classical antiquity.