The Book of Ezra begins by telling us that the great Persian king, Cyrus, who had ruled since 557 B.C., now reigned over the Babylonian Empire in 539 B.C. This is incidentally the year in which the captivity of the Jews in Babylon came to an end.
King Cyrus issued a remarkable decree commanding that the Jewish Temple be rebuilt at Jerusalem. We see here the unique policy of the Persians towards their subjects: rather than forcing them to assimilate Persian culture, they manifest great respect to the religions of their subjects, even to the point of returning all of the sacred and precious articles taken from the Jews by the Babylonians and rebuilding the Temple in Jerusalem.
Ezra, however, is not concerned with King Cyrus’s politics so much as the restoration of worship in the Temple, which was destroyed in 586 B.C. Jeremiah prophesied that it would not be rebuilt for 70 years, and indeed, it was restored in 516 B.C. Once finished, the Temple receives many of the vessels and artifacts stolen from the Jews by the Babylonians before the captivity.