Let’s review a bit:
Isaiah has three parts: Chapters 1 – 35 (which are mostly poetry), chapters 36 – 39 (which are mostly prose), and chapters 40 – 66 (which are mostly poetry again).
Chapters 1 – 35 have three parts:
Chapters 1 – 12 (which is an address specifically to Judah and ends in a psalm of joy).
Chapters 13 – 26 (which is an address of judgment against Judah and her surrounding nations, emphasizing the sovereignty of God and ending with judgment against all nations and with a psalm of joy).
Chapters 27 – 35 (which is an address against Judah, using Israel as an example and ending with judgment against all nations and a psalm of joy). Isaiah is such a long book, and so repetitive, that it’s good to be able to keep your bearings.
Chapter 34 is the address against the nations, but Edom is the nation specified to serve as the example to all other nations. Here’s the point: God uses the natural aggressive inclinations of these nations to punish his people for their sins. But make no mistake, Judah is God’s people, and though it is within the plan of God to use the nations against them, God judges them for their cruelty against His people.
How can God do this?
The answer is, God is God. He is sovereign. He will have His way. These nations could have come against Judah and disciplined her with respect and without cruelty, but they saw her vulnerability as a weakness of her God and too advantage. They would learn, much to their own chagrin and much too late, that God perceived weakness was not weakness at all, but surpassing greatness.