The territory of the modern state of Iraq was defined in 1920 as Mandatory Iraq. It is centered on Lower Mesopotamia (corresponding to historical Babylonia, later also known as Irq-i Arab) but also includes part of Upper Mesopotamia and of the Syrian Desert and the Arabian Desert.
As part of the larger Fertile Crescent, Mesopotamia saw the earliest emergence of civilization in the Neolithic (the Ubaid period) Age and formed a significant part of the Ancient Near East throughout the Bronze Age and the Iron Age (Sumerian, Akkadian, Babylonian and Assyrian). After the fall of the Neo-Babylonian Empire, Mesopotamia fell under Persian and then Greek rule. By the 3rd century, when it was once again under Persian (Sassanid) control, the earlier population was increasingly displaced by Arabs, and the Arabic name al-Irq dates to about this time.
The Sassanid Empire was destroyed by the Islamic conquests and displaced by the Rashidun Caliphate in the 7th century. Baghdad became the center of the "Islamic Golden Age" under the Abbasid Caliphate during the 9th century. Baghdad's rapid growth stagnated in the 10th century due to the Buwayhid and Seljuq invasions, but it remained of central importance until the Mongol invasion of 1258. After this, Iraq became a province of the Turco-Mongol Ilkhanate and declined in importance. After the disintegration of the Ilkhanate, Iraq was ruled by the Jalairids and Kara Koyunlu until its eventual absorption into the Ottoman Empire in the 16th century, intermittently falling under Iranian Safavid and Mamluk control.