Isaiah 13-23, the next major section of Isaiah after 1-12, teach
a primary and central truth (that are announced as prophecy or oracles): God's kingdom is the world. God's sovereignty is not something that is nebulous but actual and real. Together these chapters form a prelude to the world visions of ch. 24-27. It is also an interlude between the prediction of the Assyrian crisis in ch. 1-12 and its onset in ch. 28-39.
Focus on Babylon. Isa 13:1 begins a new section of Isaiah. The oracles in ch. 13-23 focus on the destruction of several nations (mostly foreign nations; all the nations surrounding and including Judah), and is thus set apart from ch. 1-12, which primarily addresses Judah. The judgment focuses on Babylon more than the other nations mentioned. (There are 55 verses dealing with the judgment of Babylon, but not more than 38 for any other nation.) Though other views are possible, it appears that ch.13-23 forms a unit devoted to prophecies against specific nations.
A message for God's people. Given that Israel's leadership exhibited a tendency to cast their lot with the nations, it may be that these oracles were designed to remind Israel's leaders that partnering with foreign powers was futile. The oracles would also encourage the remnant, those within Israel who trusted the Lord. No nation, regardless of its perceived power, can stand against God.