Esdras 6:22

22. Turned the heart of the king of Assyria The Persian monarch is here called king of Assyria, because he ruled over all the provinces that were comprised in the former Assyrian empire, and these provinces now constituted the greater part of the Persian empire. For the same or a similar reason, Cyrus is called in Ezra 5:13, and Artaxerxes in Nehemiah 13:6, king of Babylon, whereas they also like Darius, were kings of Persia. The king of Assyria may here be understood of both Cyrus and Darius, for they both took measures to strengthen their hands in the work of the house of God. Both being adherents of the comparatively pure monotheism of the ancient Persians, they had a natural sympathy for the religious system of the Jews. Compare notes on Ezra 1:2.