Later, as a nation and empire that came to control all of the Fertile Crescent, Egypt and much of Anatolia, the term "Assyria proper" referred to roughly the northern half of Mesopotamia (the southern half being Babylonia), with Nineveh as its capital.
The Assyrian kings controlled a large kingdom at three different times in history. These are called the Old (20th to 15th c. BC), Middle (15th to 10th c. BC), and Neo-Assyrian (911 – 612 BC) kingdoms, or periods, of which the last is the most well known and best documented.
The Assyrian homeland was located near a mountainous region, extending along the Tigris as far as the high Gordiaean or Carduchian mountain range of Armenia, sometimes known as the "Mountains of Ashur".
Assyrians invented excavation to undermine city walls, battering rams to knock down gates, as well as the concept of a corps of engineers, who bridged rivers with pontoons or provided soldiers with inflatable skins for swimming.
Of the early history of the kingdom of Assyria, little is positively known. According to some Judaeo-Christian traditions, the city of Ashur (also spelled Assur or Aššur) was founded by Ashur the son of Shem, who was deified by later generations as the city's patron god.
The upper Tigris River valley seems to have been ruled by Sumer, Akkad, and northern Babylonia in its earliest stages; once a part of Sargon the Great's empire, it was destroyed by barbarians in the Gutian period, then rebuilt, and ended up being governed as part of the Empire of the 3rd dynasty of Ur.
Like many commercial city-states in history, Assur was to a great extent an oligarchy rather than a monarchy. Authority was considered to lie with "the City", and the polity had three main centres of power — an assembly of elders, a hereditary ruler, and an eponym. The ruler presided over the assembly and carried out its decisions. He was not referred to with the usual Akkadian term for "king", šarrum; that was instead reserved for the city's patron deity Assur, of whom the ruler was the high priest. The ruler himself was only designated as "the steward of Assur" (iššiak Assur), where the term for steward is a borrowing from Sumerian ensi(k). The third centre of power was the eponym (limmum), who gave the year his name, similarly to the archons and consuls of Classical Antiquity. He was annually elected by lot and was responsible for the economic administration of the city, which included the power to detain people and confiscate property. The institution of the eponym as well as the formula iššiak Assur lingered on as ceremonial vestiges of this early system throughout the history of the Assyrian monarchy.
Ishme-Dagan inherited the kingdom, but Yasmah-Adad was overthrown, and Mari was lost. The new king of Mari allied himself with Hammurabi of Babylon. Assyria now faced the rising power of Babylon in the south. Ishme-Dagan responded by making an alliance with the enemies of Babylon, and the power struggle continued for decades.
There are dozens of Mesopotamian cuneiform texts from this period, with precise observations of solar and lunar eclipses, that have been used as 'anchors' in the various attempts to define the chronology of Babylonia and Assyria for the early second millennium, i.e., the "high", "middle", and "low" chronologies.
(Scholars variously date the beginning of the "Middle Assyrian period" to either the fall of the Old Assyrian kingdom of Shamshi-Adad I, or to the ascension of Ashur-uballit I to the throne of Assyria.)
Shalmaneser's son and successor, Tukulti-Ninurta I, deposed Kadashman-Buriash of Babylon and ruled there himself as king for seven years, taking on the old title "King of Sumer and Akkad". Another weak period for Assyria followed when Babylon revolted against Tukulti-Ninurta, and later even made Assyria tributary during the reigns of the Babylonian kings Melishipak II and Marduk-apal-iddin I.
The correct chronology of these Assyrian kings is still is much debated. There are some crucial solar eclipse records. Wikipedia's Assyrian eclipse page refers to four such eclipses. For example, the Assyrian eclipse associated with June 15, 763 BC is widely accepted by the defenders of a middle chronology, but three ignored solar eclipses from the reign of Esarhaddon would affect the calculation drastically.
The son of Ashur-resh-ishi's, Tiglath-Pileser I, may be regarded as the founder of the first Assyrian empire. In 1120 BC, he crossed the Euphrates, capturing Carchemish, and defeated the Mushki and the remnants of the Hittites — even claiming to reach the Black Sea. He advanced to the Mediterranean, subjugating Phoenicia, where he hunted wild bulls. He also marched into Babylon twice, assuming the old title "King of Sumer and Akkad", although he was unable to depose the actual king in Babylonia, where the old Kassite dynasty had now succumbed to an Elamite one.
The Middle Assyrian kingdom was well organized, and in the firm control of the king, who also functioned as the High Priest of Ashur, the state god. He had certain obligations to fulfill in the cult, and had to provide resources for the temples. The priesthood became a major power in Assyrian society. Conflicts with the priesthood are thought to have been behind the murder of king Tukulti-Ninurta I.
The main Assyrian cities of the middle period were Ashur, Kalhu (Nimrud) and Nineveh, all situated in the Tigris River valley. At the end of the Bronze Age, Nineveh was much smaller than Babylon, but still one of the world's major cities (population ca. 33,000). By the end of the Neo-Assyrian period, it had grown to a population of some 120,000, and was possibly the largest city of that time.
All free male citizens were obliged to serve in the army for a time, a system which was called the ilku-service. The Assyrian law code, notable for its repressive attitude towards women in their society, was compiled during this period.
In the Middle Assyrian period, Assyria had been a minor kingdom of northern Mesopotamia, competing for dominance with Babylonia to the south. Beginning with the campaigns of Adad-nirari II, Assyria became a great regional power, growing to be a serious threat to 25th dynasty Egypt. It began reaching the peak of its power with the reforms of Tiglath-Pileser III (ruled 745 – 727 BC). This period, which included the Sargonic dynasty, is well-referenced in several sources, including the Assyro-Babylonian Chronicles and the Hebrew Bible. Assyria finally succumbed to the rise of the neo-Babylonian Chaldean dynasty with the sack of Nineveh in 612 BC.
The utter and complete destruction of the Assyrian capitals of Nineveh and Assur by the Babylonians and Medes ensured that the bilingual elite, perhaps the few remaining still competent in Akkadian, were wiped out. By the 6th century B.C., much of the Assyrian population that survived used Aramaic and not the cuneiform Akkadian. In time, Akkadian would no longer be used by the Assyrians, although many aspects of the culture associated, such as naming with Assur, continued, and do so today.
Assyrian art preserved to the present day predominantly dates to the Neo-Assyrian period. Art depicting battle scenes, and occasionally the impaling of whole villages in gory detail, was intended to show the power of the emperor, and was generally made for propaganda purposes. These stone reliefs lined the walls in the royal palaces where foreigners were received by the king. Other stone reliefs depict the king with different deities and conducting religious ceremonies. Many stone reliefs were discovered in the royal palaces at Nimrud (Kalhu) and Khorsabad (Dur-Sharrukin). A rare discovery of metal plates belonging to wooden doors was made at Balawat (Imgur-Enlil).
Assyrian sculpture reached a high level of refinement in the Neo-Assyrian period. One prominent example is the winged bull Lamassu, or shedu that guard the entrances to the king's court. These were apotropaic meaning they were intended to ward off evil. C. W. Ceram states in The March of Archaeology that lamassi were typically sculpted with five legs so that four legs were always visible, whether the image were viewed frontally or in profile.
Since works of precious gems and metals usually do not survive the ravages of time, we are lucky to have some fine pieces of Assyrian jewelry. These were found in royal tombs at Nimrud.
There is ongoing discussion among academics over the nature of the Nimrud lens, a piece of rock crystal unearthed by Austen Henry Layard in 1850, in the Nimrud palace complex in northern Iraq. A small minority believe that it is evidence for the existence of ancient Assyrian telescopes, which could explain the great accuracy of Assyrian astronomy. Other suggestions include its use as a magnifying glass for jewellers, or as a decorative furniture inlay. The Nimrud Lens is held in the British Museum.
Classical historiographers had only retained a very dim picture of Assyria. It was remembered that there had been an Assyrian empire predating the Persian one, but all particulars were lost. Thus Jerome's Chronicon lists 36 kings of the Assyrians, beginning with Ninus, son of Belus, down to Sardanapalus, the last king of the Assyrians before the empire fell to Arbaces the Median. Almost none of these have been substantiated as historical, with the exception of the Neo-Assyrian and Babylonian rulers listed in Ptolemy's Canon, beginning with Nabonassar.
The modern discovery of Babylonia and Assyria begins with excavations in Nineveh in 1845, which revealed the library of Ashurbanipal. Decipherment of cuneiform was a formidable task that took more than a decade, but by 1857, the Royal Asiatic Society was convinced that reliable reading of cuneiform texts was possible. Assyriology has since pieced together the formerly forgotten history of Mesopotamia. In the wake of the archaeological and philological rediscovery of ancient Assyria, Assyrian nationalism has come to strongly identify with ancient Assyria.