"When word comes to Egypt, they will be in anguish at the report from Tyre." NIV translation
The nations, as represented by Egypt, would mourn the loss of the great Phoenician trading ships.
"Cross over to Tarshish; wail, you people of the island. Is this your city of revelry, the old, old city, whose feet have taken her to settle in far-off lands?" NIV translation
The first part of the prophecy dealt with the settlements on the mainland of Lebanon. Nebuchadnezzar of Babylon laid siege to the city and most of the residents fled to live on the island. Tarshish probably refers to a city in southern Spain called Tartessus which is Tarshish in Aramaic.
It seems that God was giving the people of the island city of Tyre a chance to flee to the west. Nebuchadnezzar did not take the city but it was eventually taken and leveled by Alexander the Great. It was taken by connecting the island to the mainland by a causeway which allowed the siege engines to break down the fortified walls of the island city.
"Who planned this against Tyre, the bestower of crowns, whose merchants are princes, whose traders are renowned in the earth? The Lord Almighty planned it, to bring down her pride in all her splendor and to humble all who are renowned on the earth." NIV translation
Isaiah makes it clear that this is a judgment from God and that it is a warning to all of the nations of the earth but especially to the proud. Tyre was a great city of the time and its people were respected for their business skills but God humbled her and will humble the nations of the earth.
We remember that Tyre had come under judgment for the fact that she rejoiced at the captivity of Judah and wanted to profit from that captivity. This should be a wake-up call for the rich and powerful nations of the earth as Isaiah says that Tyre was brought down to humble all of the renowned of the earth. This is talking about the proud nations that have wealth and power but do not acknowledge that it all comes from the Lord Almighty.