Why doesn't God destroy the Devil?

Fulfilled Bible prophecy, however, shows that the Devil is intensifying earth's woes because he knows that he has only "a short period of time" left to wreak havoc before being confined. (Revelation 12:7-12; 20:1-3) The end of Satan's rule will usher in a righteous new world, where tears, death, and pain "will be no more." Then, God's will shall "be done on earth as it is in heaven."—Revelation 21:1-4; Matthew 6:10, New International Version.