 The Christian west did succeed in almost entirely enforcing that a free Christian could not be enslaved, for example when a captive in war, but this itself was subject to continual improvement and was not consistently applied throughout history.The Middle Ages also witnessed the emergence of groups like the Mercedarians, who were founded for the goal of freeing Christian slaves.Although some Catholic clergy, religious orders and Popes owned slaves, and the naval galleys of the Papal States were to use captured Muslim galley slaves in particular.