Jeremiah 51:11

Gather the shields— Fill the quivers. Houbigant. Neriglissar king of Babylon having formed an alliance against the Medes, Cambyses sent his son Cyrus, with an army of thirty thousand Persians, to join the Medes, commanded by Cyaxares. This Cyaxares, king of Media, called in Scripture Darius the Mede, was the uncle of Cyrus; and it was properly his army which made the expedition against the Babylonians, Cyrus being employed as his general: Persia was then a small part of the empire of Media, and of little account till Cyrus advanced its reputation; and even then it was called the kingdom of the Medes and Persians, the Medes having still the preference. See Lowth, and Xenophon's Cyropaed. lib. 1.