Who is the Assyrian?

The Bible foretells a mysterious character called “the Assyrian” who seems to have a role in the end times war against Israel. Who is he? 

What’s odd is the Hebrew text of Micah 5:5–6 (and Isaiah 14:25, 31:8, and 52:4) lacks the definite article “the.” In other words, there is no "the Assyrian" in the Old Testament. 

The Hebrew word Assur can referred to Assyria, its capital city, or its chief deity, who was the equivalent of the Sumerian/Babylonian god Enlil (called Ellil in Akkad), El of Canaan, Dagon of the Philistines, and Milcom of Ammon—and thus Molech, the netherworld god who demanded the sacrifice of children from his followers. 

We believe the passages in Micah are an “already but not yet” prophecy, referring to the imminent conquest of the northern kingdom of Israel by Assyria, which occurred during Micah’s lifetime in 722 BC, and a future return of Assur in the end times as the Destroyer, Abaddon/Apollyon, who is released from the abyss for five months to torment those without the seal of God on their foreheads.