"the rod that struck you is broken" (14:29). Who is the rod, and who is the adder?

The chapter doesn't say. It dates the burden "in the year that King Ahaz died" (14:28), tells Philistia not to rejoice "because the rod that struck you is broken" (14:29), and says, "for out of the serpent’s root an adder will emerge, and his fruit will be a fiery flying serpent" (14:29). Later it says, "for smoke comes out of the north, and there is no straggler in his ranks" (14:31). It names no king or people for the rod, the serpent, the adder or the smoke, and these notes don't supply one from outside the Bible or work out a date. What the burden does say plainly is where refuge is: "the LORD has founded Zion, and in her the afflicted of his people will take refuge" (14:32).