'Fortified Cities' in the Bible

Now in the fourteenth year of King Hezekiah, Sennacherib king of Assyria came up against all the fortified cities of Judah and conquered them.

“Have you not heard [says the God of Israel]That I did it long ago,That I planned it in ancient times?Now I have brought it to pass,That you [king of Assyria] would [be My instrument to] turn fortified cities into ruinous heaps.