” … The oldest cult of the mother goddess, so far as our material goes, appears indeed to have been in Uruk where she is known as Nana, but we may be quite sure that the cult was never limited to one place. The special place which Nana has in the old Babylonian pantheon is probably due to the peculiar development taken by the chief deity of that centre, Anu, who as we have seen became an abstraction, the god of heaven, presiding over the upper realm of the universe. Her temple at Uruk known as E-anna “the heavenly house” and revealing the association of the goddess with Anu as a solar deity became one of the most famous in the Euphrates Valley.
It is in connection with the cult of Nana that we learn of a phase of the worship of the mother-goddess which degenerates into the obscene rites that call forth the amazement of Herodotus.  As the mother-goddess, Nana or Ishtar is not only the source of the fertility displayed by the earth and the kind, gracious mother of mankind, but also the goddess of love, the Aphrodite of Babylonia. The mysterious process of conception and the growth of the embryo in the mother’s womb gave rise at an early period to rites in connection with the cult of the mother-goddess that symbolized the fructification through the combination with the male element.
There is, however, another side to Ishtar which comes particularly to the fore in Assyria, though it is also indigenous to Babylonia. She is not only the loving mother but, as the protector of her offspring, a warlike figure armed for the fray and whose presence is felt in the midst of the battle. She appears to her favorites in dreams and encourages them to give battle. It is she who places in the hands of the rulers the weapons with which they march to victory. To Ashurbanapal she thus appears armed with bow and arrow and reassures him: “Whithersoever thou goest, I go with thee”.  As far back as the days of Hammurapi, Ishtar is thus viewed as the one who encourages her followers for contest and battle.”
Morris Jastrow, The Civilization of Babylonia and Assyria, 1915, pp. 223-4.