Once again the change between chapters should have been between verses 4 and 5 here rather than where currently broken. Not only do the first 4 verses fit better into the poetic structure set up in the previous chapter but this verse sees a change in subject. The prophecy moves from pronouncements against Israel and Judah to a condemnation of Assyria. It is in that context that Assyria is the "rod of mine anger." As noted earlier, the rod is a symbol of a weapon of attack.