"They set the tables, they spread the rugs, they eat, they drink! Get up, you officers, oil the shields!" NIV translation
This verse predicts the fact that the Babylonians would be having a giant party as their city was being compromised.
At this party, they even took articles that they had captured in Jerusalem and desecrated them as they used them to get drunk. While they were having this party, the Medes entered the city and defeated them and Darius the Mede took over their kingdom (see Daniel 5).
Instead of preparing for the battle that they knew was coming, the leaders of the Babylonians were involved in the party. God had used them as an instrument of judgment but they were now judged themselves.
"This is what the Lord says to me: 'Go, post a lookout and have him report what he sees. When he sees chariots with teams of horses, riders on donkeys or riders on camels, let him be alert, fully alert.'" NIV translation
God assures Isaiah that the Babylonians will fall just as He said. He went so far as to say that the people should post a watchman to keep an eye out for the news.
This is a reminder to us as well that, when God says that something will happen, we can watch out because it will happen.
"And the lookout shouted, 'Day after day, my Lord, I stand on the watchtower; every night I stay at my post. Look, here comes a man in a chariot with a team of horses. And he gives back the answer: "Babylon has fallen, has fallen! All the images of its gods lie shattered on the ground!"' My people who are crushed on the threshing floor, I tell you what I have heard from the Lord Almighty, from the God of Israel." NIV translation
Isaiah reassures the people of what God has shown him and the fact that those who were oppressing them would be judged.
The same type of assurance is for us, as Christians, today. Though we face discrimination many times as well as outright persecution in some areas, in the end God will pronounce judgment on those who cause it.