The text does not specify the identity of the enemies. The term could refer to those who in the past worked with the Assyrians. But more likely the term enemies
is a collective singular that refers to all Judah’s enemies.1
The Lord had earlier promised Abraham that he would possess the gate of his foes (Genesis 22:17); among the tribes, Judah in particular would clasp his enemies by the neck (Genesis 49:8). And Deuteronomy included among the blessings of the covenant the dispersing of enemies (Deuteronomy 28:7). So the enemies of Judah were to be rid of, leaving them nothing to worry over.
15 The LORD has taken away the judgments against you; he has cleared away your enemies. The King of Israel, the LORD, is in your midst; you shall never again fear evil.