'Fortified Cities' in the Bible

Declare you in Judah, and publish in Jerusalem; and say, Blow you the trumpet in the land: cry, Gather together, and say, Assemble yourselves, and let us go into the fortified cities.

And they shall eat up your harvest, and your bread, which your sons and your daughters should eat: they shall eat up your flocks and your herds: they shall eat up your vines and your fig trees: they shall impoverish your fortified cities, in which you trusted, with the sword.

Why do we sit still? assemble yourselves, and let us enter into the fortified cities, and let us be silent there: for the LORD our God has put us to silence, and given us poisoned water to drink, because we have sinned against the LORD.

When the king of Babylon's army fought against Jerusalem, and against all the cities of Judah that were left, against Lachish, and against Azekah: for these fortified cities remained of the cities of Judah.