Lest it be forgotten what we're talking about, here is the complete context from the Isaiah book:
*** ip-1 chap. 19 pp. 252-254 Jehovah Profanes the Pride of Tyre ***
19
Which political power will execute Jehovah’s judgment upon Tyre? Isaiah proclaims: "Look! The land of the Chaldeans. This is the people—Assyria did not prove to be the one—they founded her for the desert haunters. They have erected their siege towers; they have stripped bare her dwelling towers; one has set her as a crumbling ruin. Howl, you ships of Tarshish, for your stronghold has been despoiled." (Isaiah 23:13, 14) The Chaldeans—not the Assyrians—will conquer Tyre. They will erect their siege towers, level the dwelling places of Tyre, and make that stronghold of the ships of Tarshish a crumbling heap of ruins.20
True to the prophecy, not long after the fall of Jerusalem, Tyre rebels against Babylon, and Nebuchadnezzar lays siege to the city. Believing herself impregnable, Tyre resists. In the course of the siege, the heads of Babylon’s soldiers are "made bald" from the chafing of their helmets and their shoulders are "rubbed bare" from carrying materials used in the construction of siegeworks. (Ezekiel 29:18) The siege is costly to Nebuchadnezzar. The mainland city of Tyre is destroyed, yet its spoil eludes him. The bulk of the treasures of Tyre have been transferred to a small island about half a mile [0.8 km] from the shore. Lacking a fleet of ships, the Chaldean king is unable to take the island. After 13 years, Tyre capitulates, but she will survive and see the fulfillment of further prophecies."She
Must Return to Her Hire"21
Isaiah goes on to prophesy: "It must occur in that day that Tyre must be forgotten seventy years, the same as the days of one king." (Isaiah 23:15a) Following the destruction of the mainland city by the Babylonians, the island-city of Tyre will "be forgotten." True to the prophecy, for the duration of "one king"—the Babylonian Empire—the island-city of Tyre will not be an important financial power. Jehovah, through Jeremiah, includes Tyre among the nations that will be singled out to drink the wine of His rage. He says: "These nations will have to serve the king of Babylon seventy years." (Jeremiah 25:8-17, 22, 27) True, the island-city of Tyre is not subject to Babylon for a full 70 years, since the Babylonian Empire falls in 539 B.C.E. Evidently, the 70 years represents the period of Babylonia’s greatest domination—when the Babylonian royal dynasty boasts of having lifted its throne even above "the stars of God." (Isaiah 14:13) Different nations come under that domination at different times. But at the end of 70 years, that domination will crumble. What will then happen to Tyre?22
Isaiah continues: "At the end of seventy years it will happen to Tyre as in the song of a prostitute: ‘Take a harp, go around the city, O forgotten prostitute. Do your best at playing on the strings; make your songs many, in order that you may be remembered.’ And it must occur at the end of seventy years that Jehovah will turn his attention to Tyre, and she must return to her hire and commit prostitution with all the kingdoms of the earth upon the surface of the ground."—Isaiah 23:15b-17.23
Following the fall of Babylon in 539 B.C.E., Phoenicia becomes a satrapy of the Medo-Persian Empire. The Persian monarch, Cyrus the Great, is a tolerant ruler. Under this new rulership, Tyre will resume her former activity and try hard to regain recognition as a world commercial center—just as a prostitute who has been forgotten and has lost her clientele seeks to attract new clients by going around the city, playing her harp and singing her songs. Will Tyre succeed? Yes, Jehovah will grant her success. In time, the island-city will become so prosperous that toward the end of the sixth century B.C.E., the prophet Zechariah will say: "Tyre proceeded to build a rampart for herself, and to pile up silver like dust and gold like the mire of the streets."—Zechariah 9:3.