This was the sixth warning of woe (see study note on Isaiah 28:1–33:24).
Although the Hebrew text does not specifically name Assyria as the object of the prophecy in this chapter, Isaiah likely referred to Assyria. They were the destroyer closest at the time the prophecy was written. The prophecy applies to anyone who tries to destroy God's people, including the Babylonians (see Isaiah 13–14).
When you have finished betraying: Wicked nations often break political agreements when these deals no longer benefit them.