The custom of enslaving prisoners of war was totally extinguished in the thirteenth century by the prevailing influence of Christianity; but it might be proved, from frequent passages of Gregory of Tours, etc., that it was practised without censure under the Merovingian race; and even Grotius himself (de Jure Belli et Pacis, 1. iii. c. 7), as well as his commentator Barbeyrac, have laboured to reconcile it with the laws of nature and reason.