Cyrus' empire had extended into Babylon, and his conquest of the region ended the Babylonian captivity. He issued the "Edict of Restoration" which allowed the Israelites to return to the Promised Land, and is one of the more securely located historical events in the Bible:
Pasargadae and Mausoleum of Cyrus the Great in Danger of Destruction - CAIS:
Now in the first year of Cyrus king of Persia, that the word of the LORD by the mouth of Jeremiah might be fulfilled, the LORD stirred up the spirit of Cyrus king of Persia, that he made a proclamation throughout all his kingdom, and put it also in writing, saying,
2 Thus saith Cyrus king of Persia, The LORD God of heaven hath given me all the kingdoms of the earth; and he hath charged me to build him an house at Jerusalem, which is in Judah.
3 Who is there among you of all his people? his God be with him, and let him go up to Jerusalem, which is in Judah, and build the house of the LORD God of Israel, (he is the God,) which is in Jerusalem.