They will strictly besiege her, as keepers of a field will be careful who go in and who go out, Zec_12:2; they will watch that none go in to relieve them, and also that none get out to escape: see 2Ch_16:1.
Because she hath been rebellious: God doth not threaten his judgments only, but he labours to convince them that there is a sufficient reason for it, both here and in the next verse.