Licinius was a partner and rival to Constantine the Great, serving as the Eastern Emperor of Rome. His marriage to Constantine’s half-sister Constantia forestalled civil war. The wedding provided the backdrop for one of Constantine’s greatest accomplishments, the Edict of Milan, which legalized Christianity in the Empire. The honeymoon did not last. In time, Licinius, too, was executed on the orders of his brother-in-law—hung to death after his defeat at the Battle of Chrysopolis.