"When he [the writer] discussed the problems of the building of the temple in 4:1-5, it reminded him of later similar troubles with the rebuilding of the wall of Jerusalem, and so 4:6-23 has been inserted, almost parenthetically, before the argument of the building of the temple has again been taken up in 4:24ff. (already noted by C. F. Keil in the last [nineteenth] century)."71
This king of Persia, whose Greek name was Xerxes, was the man Esther married. He ruled from 486 to 464 B.C. Since the restoration Jews completed the temple in 515 B.C. (6:15) this verse shows that the neighbors of the returned exiles continued to oppose them long after they had finished rebuilding the temple.
"Without this foretaste of history to reveal the full seriousness of the opposition, we would not properly appreciate the achievements recorded in the next two chapters (5 and 6) nor the dangers hidden in the mixed marriages which Ezra would set himself to stamp out (chaps. 7-10)."72