Historical context: Isaiah 45 is addressed to Cyrus, a pagan king — God asserting universal sovereignty

Isaiah 45 is addressed to Cyrus the Great, a pagan Persian king named by God before his birth, whom God would use to return Israel from Babylonian captivity. God is distinguishing himself from the pagan gods and claiming sovereignty over all things — over light and darkness, peace and calamity. This is a polemic against polytheism: the nations had different gods for day, night, war, peace; God declares he alone controls all of these. The broader context of Isaiah makes the same argument throughout.