Late Bronze Age
The original homeland of the Kassites is not well established but appears to have been located in the Zagros Mountains, in what is now the Lorestan Province of Iran. However, the Kassites were—like the Elamites, Gutians and Manneans who preceded them—linguistically unrelated to the Iranian-speaking peoples who came to dominate the region a millennium later. They first appeared in the annals of history in the 18th century BC when they attacked Babylonia in the 9th year of the reign of Samsu-iluna (reigned c. 1749–1712 BC), the son of Hammurabi. Samsu-iluna repelled them, as did Abi-Eshuh, but they subsequently gained control of Babylonia c. 1570 BC some 25 years after the fall of Babylon to the Hittites in c. 1595 BC, and went on to conquer the southern part of Mesopotamia, roughly corresponding to ancient Sumer and known as the Dynasty of the Sealand by c. 1520 BC. The Hittites had carried off the idol of the god Marduk, but the Kassite rulers regained possession, returned Marduk to Babylon, and made him the equal of the Kassite Shuqamuna. The circumstances of their rise to power are unknown, due to a lack of documentation from this so-called “Dark Age” period of widespread dislocation. No inscription or document in the Kassite language has been preserved, an absence that cannot be purely accidental, suggesting a severe regression of literacy in official circles. Babylon under Kassite rulers, who renamed the city Karanduniash, re-emerged as a political and military power in Mesopotamia. A newly built capital city Dur-Kurigalzu was named in honour of Kurigalzu I (c. early 14th century BC).

Their success was built upon the relative political stability that the Kassite monarchs achieved. They ruled Babylonia practically without interruption for almost four hundred years—the longest rule by any dynasty in Babylonian history.

The transformation of southern Mesopotamia into a territorial state, rather than a network of allied or combative city-states, made Babylonia an international power, although it was often overshadowed by its northern neighbour, Assyria and by Elam to the east. Kassite kings established trade and diplomacy with Assyria. Puzur-Ashur III of Assyria and Burna-Buriash I signed a treaty agreeing on the border between the two states in the mid-16th century BC, Egypt, Elam, and the Hittites, and the Kassite royal house intermarried with their royal families. There were foreign merchants in Babylon and other cities, and Babylonian merchants were active from Egypt (a major source of Nubian gold) to Assyria and Anatolia. Kassite weights and seals, the packet-identifying and measuring tools of commerce, have been found in as far afield as Thebes in Greece, in southern Armenia, and even in the Uluburun shipwreck off the southern coast of today’s Turkey.

A further treaty between Kurigalzu I and Ashur-bel-nisheshu of Assyria was agreed in the mid-15th century BC. However, Babylonia found itself under attack and domination from Assyria for much of the next few centuries after the accession of Ashur-uballit I in 1365 BC who made Assyria (along with the Hittites and Egyptians) the major power in the Near East. Babylon was sacked by the Assyrian king Ashur-uballit I (1365–1330 BC)) in the 1360s after the Kassite king in Babylon who was married to the daughter of Ashur-uballit was murdered. Ashur-uballit promptly marched into Babylonia and avenged his son-in-law, deposing the king and installing Kurigalzu II of the royal Kassite line as king there. His successor Enlil-nirari (1330–1319 BC) also attacked Babylonia and his great-grandson Adad-nirari I (1307–1275 BC) annexed Babylonian territory when he became king. Tukulti-Ninurta I (1244–1208 BC) not content with merely dominating Babylonia went further, conquering Babylonia, deposing Kashtiliash IV and ruling there for eight years in person from 1235 BC to 1227 BC.

The Kassite kings maintained control of their realm through a network of provinces administered by governors. Almost equal with the royal cities of Babylon and Dur-Kurigalzu, the revived city of Nippur was the most important provincial centre. Nippur, the formerly great city, which had been virtually abandoned c. 1730 BC, was rebuilt in the Kassite period, with temples meticulously re-built on their old foundations. In fact, under the Kassite government, the governor of Nippur, who took the Sumerian-derived title of Guennakku, ruled as a sort of secondary and lesser king. The prestige of Nippur was enough for a series of 13th-century BC Kassite kings to reassume the title ‘governor of Nippur’ for themselves.

Other important centres during the Kassite period were Larsa, Sippar and Susa. After the Kassite dynasty was overthrown in 1155 BC, the system of provincial administration continued and the country remained united under the succeeding rule, the Second Dynasty of Isin.

Documentation of the Kassite period depends heavily on the scattered and disarticulated tablets from Nippur, where thousands of tablets and fragments have been excavated. They include administrative and legal texts, letters, seal inscriptions, kudurrus (land grants and administrative regulations), private votive inscriptions, and even a literary text (usually identified as a fragment of a historical epic).

Kassite king Meli-Shipak II on his throne on a kudurru-Land grant to Ḫunnubat-Nanaya. The eight-pointed star was Inanna-Ishtar’s most common symbol. Here it is shown alongside the solar disk of her brother Shamash (Sumerian Utu) and the crescent moon of her father Sin (Sumerian Nanna) on a boundary stone of Meli-Shipak II, dating to the twelfth century BC.

“Kassite rulers in Babylon were also scrupulous to follow existing forms of expression, and the public and private patterns of behaviour “and even went beyond that—as zealous neophytes do, or outsiders, who take up a superior civilization—by favouring an extremely conservative attitude, at least in palace circles.” (Oppenheim 1964, p. 62).

The Elamites conquered Babylonia in the 12th century BC, thus ending the Kassite state. The last Kassite king, Enlil-nadin-ahi, was taken to Susa and imprisoned there, where he also died.

Iron Age
The Kassites did briefly regain control over Babylonia with Dynasty V (1025–1004 BC); however, they were deposed once more, this time by an Aramean dynasty.

Kassites survived as a distinct ethnic group in the mountains of Lorestan (Luristan) long after the Kassite state collapsed. Babylonian records describe how the Assyrian king Sennacherib on his eastern campaign of 702 BC subdued the Kassites in a battle near Hulwan, Iran.

Herodotus and other ancient Greek writers sometimes referred to the region around Susa as “Cissia”, a variant of the Kassite name. However, it is not clear if Kassites were actually living in that region so late.

During the later Achaemenid period, the Kassites, referred to as “Kossaei”, lived in the mountains to the east of Media and were one of several “predatory” mountain tribes that regularly extracted “gifts” from the Achaemenid Persians, according to a citation of Nearchus by Strabo.

But Kassites again fought on the Persian side in the Battle of Gaugamela in 331 BC, in which the Persian Empire fell to Alexander the Great, according to Diodorus Siculus (17.59) (who called them “Kossaei”) and Curtius Rufus (4.12) (who called them “inhabitants of the Cossaean mountains”). According to Strabo’s citation of Nearchus, Alexander later separately attacked the Kassites “in the winter”, after which they stopped their tribute-seeking raids.

Strabo also wrote that the “Kossaei” contributed 13,000 archers to the army of Elymais in a war against Susa and Babylon. This statement is hard to understand, as Babylon had lost importance under Seleucid rule by the time Elymais emerged around 160 BC. If “Babylon” is understood to mean the Seleucids, then this battle would have occurred sometime between the emergence of Elymais and Strabo’s death around 25 AD. If “Elymais” is understood to mean Elam, then the battle probably occurred in the 6th century BC. Susa was the capital of Elam and later of Elymais, so Strabo’s statement implies that the Kassites intervened to support a particular group within Elam or Elymais against their own capital, which at that moment was apparently allied with or subject to Babylon or the Seleucids.

The latest evidence of Kassite culture is a reference by the 2nd-century geographer Ptolemy, who described “Kossaei” as living in the Susa region, adjacent to the “Elymeans”. This could represent one of many cases where Ptolemy relied on out-of-date sources.

It is believed that the name of the Kassites is preserved in the name of the Kashgan River, in Lorestan.