For the hypothetical planet Marduk, see Marduk (planet).
Marduk is a late generation god from ancient Mesopotamia, and the patron deity of the city of Babylon.
When Babylon became the capital of Mesopotamia, the patron deity of Babylon was elevated to the level of supreme god. In order to explain how Marduk seized power, Enuma Elish was written, which tells the story of Marduk's birth, heroic deeds, and becoming the ruler of the gods. This can be viewed as a form of Mesopotamian apologetics.
In Enuma Elish a civil war between the gods was growing to a climatic battle. The Anunnaki gods gathered together to find one god who could defeat the gods rising against them. Marduk, a very young god, answered the call, and was promised the position of head god.
When he killed his enemy he "Wrested from him the Tablet of Destinies, wrongfully his," and assumed his new position. Under his reign humans were created to bear the burdens of life so the gods could be at leisure.
The following entry was originally from the 1911 Encyclopedia Britannica.
Marduk (Bibl. Merodach) was the name of the patron deity of the city of Babylon, who, when Babylon permanently became the political centre of the united states of the Euphrates valley under Khammurabi (c. 2250 BC), rose to the position of the head of the Babylonian pantheon.
His original character was that of a solar deity, and he personifies more specifically the sun of the spring-time who conquers the storms of the winter season. He was thus fitted to become the god who triumphs over chaos that reigned in the beginning of time.
This earlier Marduk, however, was effaced by the reflex of the political development through which the Euphrates valley passed and which led to imbuing him with traits belonging to gods who at an earlier period were recognized as the heads of the pantheon. There are more particularly two gods--Ea and Bel--whose powers and attributes pass over to Marduk. In the case of Ea the transfer proceeds pacifically and without involving the effacement of the older god. Marduk is viewed as the son of Ea. The father voluntarily recognizes the superiority of the son and hands over to him the control of humanity. This association of Marduk and Ea, while indicating primarily the passing of the supremacy once enjoyed by Eridu to Babylon as a religious and political centre, may also reflect an early dependence of Babylon upon Eridu, not necessarily of a political character but, in view of the spread of culture in the Euphrates valley from the south to the north, the recognition of Eridu as the older centre on the part of the younger one.
At all events, traces of a cult of Marduk at Eridu are to be noted in the religious literature, and the most reasonable explanation for the existence of a god Marduk in Eridu is to assume that Babylon in this way paid its homage to the old settlement at the head of the Persian Gulf.
While the relationship between Ea and Marduk is thus marked by harmony and an amicable abdication on the part of the father in favour of his son, Marduk's absorption of the power and prerogatives of Bel of Nippur was at the expense of the latter’s prestige. After the days of Khammurabi, the cult of Marduk eclipses that of Bel, and although during the five centuries of Cassite control in Babylonia (c. 1750—1200 BC), Nippur and the cult of the older Bel enjoy a period of renaissance, when the reaction ensued it marked the definite and permanent triumph of Marduk over Bel until the end of the Babylonian empire. The only serious rival to Marduk after 1200 BC is Assur in Assyria. In the south Marduk reigns supreme, and his supremacy is indicated most significantly by making him the Bel, "the lord," par excellence.
The old myths in which Bel of Nippur was celebrated as the hero were transformed by the priests of Babylon in the interestMarduk Seizes power
1911 Encyclopedia Britannica Article