A form of commerce in slaves that existed from earliest times in the Arabian peninsular. The Prophet Muhammad forbade his followers to enslave Muslims, but did not free slave converts. His legislation insisted on humane treatment and gave slaves rights against oppressive masters. In early Islam slaves were recruited from prisoners-of-war (including women and children) and were acquired by raiding and by purchase in Eastern and Southern Europe, Central Asia, and Central, East, and West Africa. Under the caliphs the trade was brisk. Slaves served a variety of purposes: agricultural, mining, domestic, and clerical, and for military service. Many slave women employed as concubines were given the rights of wives. Men and children often received vocational training after capture. Through international pressure, the trade was largely abolished during the 19th century. (See also slavery.)