The northeastern part of Mesopotamia (modern Iraq), named after the central city of Assur on the Tigris. The first Assyrian state originated in the 18th century BC, and a few centuries later an important expansion began. Pharaoh Tuthmosis III (18th Dynasty) was able to penetrate as far as the eastern bank of the Euphrates, thus virtually forcing Assyria to conduct diplomatic relations with Egypt. Various other pharaohs also maintained contact with Assyria, for example Amenhotep III and Amenhotep IV/Akhenaten. In the first half of the first millenium BC Assyria conquered a large part of the Near East. In 671 BC the army of King Esarhaddon invaded Egypt, but Pharaoh Taharka (25th Dynasty) was able to repulse them immediately. A short time later, however, in 669 BC, the army under Assurbanipal again invaded the Delta and a few years later penetrated as far as Thebes. The Assyrians installed Psammetichus I as a vassal ruler, but he was able to free himself of their yoke to a great extent and henceforth ruled independently. This Egyptian freedom lasted until 525 BC, when the Persians under Cambyses invaded the country.