Babylon = Assyria

In the OT, “Babylon” and “Assyria” are sometimes used interchangeably of the same political power:

• The two powers spoke essentially the same language. The cultures, religions, economics, and ambitions of these two cities were practically identical.
• In the time of Isaiah, Assyria conquered Babylon, and then in the time of Zedekiah Babylon destroyed Assyria.
• Sennacherib had captured and subjugated Babylon. “King of Babylon” = one of titles of kings of Assyria. Names are switched in Ezr 6:22; Lam 5:6; Zep 10:10,11; Isa 14:4,25; Mic 5:5; 4:10. Cp 2Ch 33:11; Amo 5:27 with Act 7:43.
• Nahum read Isa 47 as prophecy of Assyria, not Babylon. He was Isaiah’s contemporary: cp Nah 3:5,4,16 with Isa 47:2,3,9,15; Nah 1:15 with Isa 52:7; Nah 1:13 with Isa 47:6; Zep 2:13,15 with Isa 47:8; and Zep 2:14,15 with Isa 13:21,22.
• Nahum also alludes to the “whoredoms, witchcraft, etc” of “Babylon” (Nah 3:4,5,16 = Isa 47:3,9,15) when his subject is still the end of Nineveh.
• In the reign of Josiah, Pharaoh-necho went against “the king of Assyria” at Carchemish (2Ki 23:29) — actually Nabopolassar, the father of Nebuchadnezzar of Babylon.
• Stephen interchanged “Damascus” and “Babylon” in Act 7:43.
• In Isa 13:19 and often in Isa 14, “Babylon” is represented as the supreme world-power, exercising a cruel tyranny over many nations and esp over Israel. But in Isaiah’s day, Babylon was either a conquered state of the Assyrian empire or was making sporadic attempts at rebellion from the Assyrian yoke. Thus the “Babylon” here must be “Nineveh/Assyria”.
• The kings of Assyria took special pride in their domination of Babylon. Sargon records as one of his royal titles: “Viceroy of the gods of Babylon”. Tiglath-pileser proudly called himself “King of Babylon”.