Chapter 31: the fall of Egypt, Assyria, and salvation of Jerusalem

Not rely on Egypt for help: Woe onto those who go down to Egypt to seek their aid to help them in the war against Assyria, rather than rely on G-d. G-d will not revoke his decree to exile the 10 tribes despite all the attempts to get Egypt to intervene. G-d will punish those from Israel who try to seek the Egyptian intervention and will also punish the Egyptians who come to help.
Protecting Jerusalem: G-d will protect Jerusalem from the surrounding Army of Assyria.
A call for repentance: The prophet calls upon all the residents of Jerusalem to return to G-d. Every man will despise the gold and silver deities that they made.
The fall of Assyria: Assyria will fall not by the sword of man but through an angel. They will flee from the sword and their choices soldiers will be placed in slavery to their enemies. An oven and fire have already been prepared in Jerusalem to burn the enemy soldiers of Assyria.

Yeshayahu/Isaiah Chapter 31: The fall of Egypt, Assyria, and salvation of Jerusalem