The cities of Manasseh - Even those who were under the government of the Israelitish king permitted their idols and places of idolatry to be hewn down and destroyed: after the truth was declared and acknowledged, the spade and the axe were employed to complete the reformation.
The power of Assyria being now (629-624 B.C.) greatly weakened, if not completely broken, Josiah aimed not merely at a religious reformation, but at a restoration of the kingdom to its ancient limits (see the 2 Kings 23:19 note).
With their mattocks - Or “in their desolate places” (compare Psalm 109:10). Another reading gives the sense, “he proved their house round about.”