Isaiah 45 – Cyrus the Messiah?

OK, here’s an interesting note from JSB: In 45:1 the text says, “Thus said the Lord to Cyrus, His anointed one…” Here the word translated to His anointed one is the same word translated elsewhere as Messiah. The author notably uses this word in reference to Cyrus, not of a king from the line of David. Two thoughts come to mind: Isaiah son of Amoz had clearly believed that the line of David would not be broken, that no one else would properly be called King. Secondly, the JSB notes that the Hebrew Bible (our Old Testament) exclusively uses the word Messiah in reference to the currently reigning king, never to indicate a future ideal one. I guess that comment depends upon the decision as to whether ch. 45 was written during the time of Cyrus or nearly 200 years prior.