Slavery in the Muslim world first developed out of the slavery practices of pre-Islamic Arabia, and were at times radically different, depending on social-political factors such as the Arab slave trade. Two rough estimates by scholars of the number of slaves held over twelve centuries in Muslim lands are 11.5 million and 14 million.
Because internal growth of the slave population was not enough to fulfill the demand in Muslim society, massive numbers of non-Muslim slaves were imported, resulting in enormous suffering and loss of life from their capture and transportation.
The Arab slave trade was most active in West Asia, North Africa, and Southeast Africa. In the early 20th century (post World War I), slavery was gradually outlawed and suppressed in Muslim lands, largely due to pressure exerted by Western nations such as Britain and France. Among the last states to abolish slavery were Saudi Arabia and Yemen, which abolished slavery in 1962 under pressure from Britain; Oman in 1970, and Mauritania in 1905, 1981, and again in August 2007. However, slavery claiming the sanction of Islam is documented presently in the predominantly Islamic countries of Chad, Mauritania, Niger, Mali, and Sudan.