The slave trade recommenced in 1455 in Africa. The Pope gave justification to enslave non-Christians in a papal bull.[Citation Needed] It became an important part of Africa's economy. It did not come to an end until 1800-1865 with the work of Christians; William Wilberforce and John Wesley.[Citation Needed] The United States passed the 13th Amendment in response to it.
World History Lecture Eight can be used for more information.