Followed by the collapse of the Akkadian Empire around 2154 BC, within 180 years of its foundation, the Akkadian people split into two major Akkadian speaking nations, Assyria in the north, and Babylonia in the south. Assyria, named after the ancient city of Ashur, located on the west bank of the River Tigris, in the northeast of Babylon in the northern Mesopotamia, was one of the Akkadian-speaking city states under the Akkadian Empire, which flourished due to their trade with Anatolia.

However, although the Semitic Assyrians originally spoke and wrote Akkadian, later they adopted the easier to use Aramaic language, which became more popular. According to a Biblical story, Ashur was founded after the Great Flood by a man named Ashur son of Shem, the son of Noah, who subsequently founded the other important Assyrian cities. However, some also believe that sometime in the 3rd millennium BC, the city was named after the name of the deity of the same name, whose name is also the origin for Assyria. Nevertheless, although the city state of Ashur, known as Subartu to the Sumerians, had a relatively humble beginning early in the second millennium BC, within several hundred years of the collapse of the Akkadian Empire, Assyria became a major empire in Mesopotamia. In the beginning of the 7th century BC, Assyria was at the height of its power, when the entire Fertile Crescent was under the control of the Assyrian Emperors, and the Assyrian Empire was stretched from Cyprus in the Mediterranean Sea to Persia, and from the regions of the Caucasus Mountains, comprising Armenia, Georgia, Azerbaijan, to the Arabian Peninsula and Egypt. During that period, Assyria was also at the height of technological, scientific, and cultural achievements. However, the Assyrian Empire collapsed in 609 BC, when the last Assyrian ruler, Ashur-Uballit II tried to rally the Assyrian army at Harran in the west, but was defeated by the assault of the Babylonians from southern Mesopotamia and the Medes, who were to establish a kingdom in Iran.

The scholars have roughly divided the history of Assyria into three periods comprising the Old Assyrian Period that continued from the late 21st to 18th century BC, the Middle Assyrian Period, continuing from 1365 to 1056 AD, and the Neo-Assyrian Period, from 911 to 612 BC, which are roughly corresponding to the Middle Bronze Age, Late Bronze Age, and the Early Iron Age, respectively.

The Old Assyrian period, extended from 2000 to 1600 BC, traditionally defined as the time between the fall of the Ur III empire, when the city of Ashur was flourishing with a distinctive culture, separate from that of southern Mesopotamia.

It is evident from the inscriptions of Ilusuma and Erisum I, that during that time, the early rulers of Ashur took measures to attract foreign traders and to facilitate the exchange of goods. Accordingly, the merchants from Ashur undertook trade between the city and the kingdoms across Central Anatolia, which is evident from the textual record of some 24,000 cuneiform tablets, most of which were discovered in the lower town of Kanesh, modern-day Kültepe, located in northern Cappadocia, Turkey. Trade with Anatolia also provided the Assyrians with raw materials from which they crafted the iron weapons for the Assyrian military, which proved to be a decisive advantage in their campaigns to conquer the entire region of the Middle East, and establishing colonies in Asia Minor and the Levant, and also asserting itself over southern Mesopotamia, under king Ilushuma. However, from the late 19th century BC, Assyria came into conflict with the newly created state of Babylonia, which eventually eclipsed the older Sumero-Akkadian states in the south, such as Ur, Isin, Larsa and Kish.

Assyria experienced fluctuating fortunes in the Middle Assyrian Period (1365-1056 BC), when the Kingdom of Mittani rose from the area of eastern Anatolia and by the 14th century BC, held power in that region of Mesopotamia, replacing the Assyrian control.

Nevertheless, the Assyrians revived during the reign of Ashur-Uballit, who extended Assyrian dominance over the rich farming lands of Nineveh and Arbela to the north. The next two kings succeeding Uballit maintained the kingdom, without further extension, until Adad-nirari I (1307–1275 BC), drove out the Hittites, conquering their major strongholds, and expanded the Assyrian power stretched to the Euphrates and the borders of the Hittite Empire. In fact, during the Middle Assyrian Empire, Assyria reached its peak under the warrior king Tukulti-Ninurta I (1244–1208 BC), who defeated the ruler of Babylonia, plundered the sacred temples of Babylon, installed puppet kings to govern the region for some thirty-two years, and with the plundered wealth from the temples, constructed a new royal palace on the other side of the Tigris from Ashur, and named it Kar-Tukulti-Ninurta. But as the Assyrians and Babylonians shared many of the same deities, his desecration of the temples of Babylon, as well as plundering god’s wealth, was deemed as an offence against the gods, for which the court officials, along with his sons rebelled against him, and he was assassinated in his palace, probably by one of his sons, Ashur-Nadin-Apli, who succeeded the throne. Later, Tiglath Pileser I (1114–1076 BC) managed to maintain the core of the empire around Ashur but was unsuccessful to drive away the Aramaeans and Amorites completely from the borders. Ultimately, by the end of the second millennium BC, the Aramaean expansion resulted in the loss of much Assyrian territory in Upper Mesopotamia, and the Assyrian Empire gradually started to shrink due to the repeated attacks from outside and rebellions from within, and entered a period of stagnancy, in which they held what they could of the empire together but could do nothing more than that.

During the Neo-Assyrian Period (912-612 BC), the final stage of the Assyrian Empire that began with the accession of Adad-nirari II, and described by many as the first world empire in history, the Assyrians dominated a vast area, stretched throughout Mesopotamia, the Levant, Egypt, Anatolia, and into parts of Persia and Arabia, creating the largest empire the world had seen at that time. During that period, the Assyrians fielded the most effective fighting force in the world, equipped with their novel tactics in battle, and armed with iron weapons, which were superior to the bronze weapons of their enemies, making them invincible in battles. For the first time in history, they also had a separate engineering unit, which helped their army to set up ladders, fill in the moats, and dig tunnels, enabling their soldiers to get into the walled cities of their enemies. Apart from that, they were also among the first to build chariots, which provided greater protection on the battlefield. Nevertheless, it is also the period, when the Assyrian Empire earned their infamous reputation for cruelty and ruthlessness.

Although Assyria is mainly remembered for its military victories, and technological advancements, the Assyrians also left behind a great deal of art and architecture, which include several artefacts, relief carvings, narrative art, Lamassu statues, cylinder seals, palaces, and ziggurats. However, like many other strongly patriarchal societies, women in Assyria were effectively treated as second class citizens, their sexuality was tightly controlled by their families, and a woman’s perceived value mostly depended on her supposed role as an incubator of male seed.

However, although Assyria was at the height of its power during the Neo-Assyrian Period, persistent difficulties to control Babylonia soon developed into a major problem and finally, the Assyrian empire collapsed at the end of the seventh century under the assault of Babylonians from southern Mesopotamia and the Medes, who destroyed Nimrud twice, first in 614 and again in 612 BC. Ultimately, with the fall of Ashur and Nineveh, Assyrian rule in the Near East came to an end in 609 BC. The site remained largely unoccupied for centuries until the Sassanian period, with only a scattering of Assyrians living amid the ruins. However, designated as a UNESCO World Heritage Site in 2003, the archaeological site is protected with its fortifications, temples, and palaces.