Jews were taken away from Jerusalem and held captive in Babylon, 597-581 B.C.
The prophet Jeremiah wrote in chapter 25:
“And it shall come to pass, when seventy years are accomplished, that I will punish the king of Babylon, and that nation, saith the Lord.”
And Jeremiah wrote in chapter 29:
“For thus saith the Lord, That after seventy years be accomplished at Babylon I will visit you, and perform my good word toward you, in causing you to return to this place.”
The prophet Daniel read Jeremiah’s prophecy and wrote in chapter 9:
“In the first year of his reign I Daniel understood by books the number of the years, whereof the word of the Lord came to Jeremiah the prophet, that he would accomplish seventy years in the desolations of Jerusalem.”
In 539 B.C., Cyrus of Persia captured Babylon, the ancient world’s largest city. Shortly after, Cyrus let Jews return to Jerusalem after 70 years of captivity.