Cyrus the Anointed and the Way Prepared for the King
Old Testament: Isaias 45:1
Thus saith the Lord to my anointed Cyrus, whose right hand I have taken hold of, to subdue nations before his face, and to turn the backs of kings, and to open the doors before him, and the gates shall not be shut.
New Testament: Apocalypse 16:12
And the sixth angel poured out his vial upon that great river Euphrates; and dried up the water thereof, that a way might be prepared for the kings from the rising of the sun.
The connection
Cyrus, a pagan Persian king, receives a title no other Gentile ruler is given in Scripture: "my anointed" (Isaias 45:1), the Hebrew mashiach that becomes, in Greek, Christos. God takes his hand, subdues nations before him, and opens gates that will not be shut, all so that Cyrus can conquer Babylon and release Israel from seventy years of captivity, becoming, unknowingly, an instrument of the very deliverance he did not worship. Historically Cyrus took Babylon by diverting the Euphrates itself, marching his army into the city along the dried riverbed under the walls, a maneuver ancient historians record in some detail. The Apocalypse reaches for the same image at the sixth vial: the great river Euphrates dried up "that a way might be prepared for the kings from the rising of the sun" (Apocalypse 16:12). The verse is deliberately poised between two readings that do not cancel each other: a repetition of Cyrus's deliverance, the way prepared for a rescuing king, or the unleashing of a hostile army for the final battle. Judgment on the false Babylon and deliverance for the true Jerusalem are, in the end, the same event seen from two sides.
Moral sense
Recognise God's hand even in instruments that don't know they're being used; providence doesn't wait for its agents to have faith, and neither should our expectation of where deliverance might come from.
Anagogical sense
Whichever way the sixth vial's ambiguity resolves, both readings converge on the same last things: the definitive fall of every Babylon and the final, unhindered road home for the people still waiting to be released.
Catechism of the Catholic Church, paragraph 436.