Medieval serfdom was only a small step above slavery.
Long before the world even heard of the United States, slavery was ongoing and VERY lucrative to slave trading individuals and governments.
None of it could have taken place at all without the eager and voluntary participation of African natives themselves.
Without good maps (any maps), considering the diseases, terrain, weather, brutal inter-tribal warfare, language barriers and everything else, no one would have even considered slaving as an enterprise. All these obstacles were mitigated by African native tribal chiefs and others who knew the continent and could perpetually deliver masses of their own brethren to coastal ports for export.
Yes...it was very lucrative for THEM and for Europeans and others who engaged in slave trading.
Read the loophole in the 13th.
It was really the rise of the military power of the United States that put a damper on Muslims kidnapping white Europeans as slaves. Easily more than a million European Christians were made the slaves of Muslims in a couple hundred years, and perhaps several times that many.
"The fact that in Mohammedan law every woman must belong to some man as his absolute property, either as a child, a wife,
or a concubine, must delay the final extinction of slavery until the faith of Islam has ceased to be a great power among men.
IRISH: THE FORGOTTEN WHITE SLAVES
http://settingrecordstraight.blogspot.com/2015/03/irish-forgotten-white-slaves.html
Irish Sugar Slaves of Barbados
https://www.youtube.com/watch?v=Du9Py0stL14
The Black Irish of Montserrat in the Caribbean
https://www.youtube.com/watch?v=vZNEloGC1oI
The Enslavement of Whites in Early America ~ Michael Hoffman
https://www.youtube.com/watch?v=jTfjv_wFBWs&spfreload=10
Forgotten White Slaves - Irish, Scots, poor Englishmen ended up as slaves in America
https://www.youtube.com/watch?v=i66NApOZh3A&spfreload=10
ML/NJ ("Honest Yankee")
America totally abolished slavery throughout all of America in less than eighty years.
Rather than celebrate the 150 years without slavery some malcontents celebrate the 80 years of slavery by picking at the scar of a healing wound.
Booker T. Washington, who rose from slavery to become the nations first widely recognized black leader, once warned against what he called "problem profiteers" among our nations black community. "
There is a class of colored people who make a business of keeping the troubles, the wrongs and the hardships of the Negro race before the public," observed Washington. "Having learned that they are able to make a living out of their troubles, they have grown into the settled habit of advertising their wrongs partly because they want sympathy and partly because it pays. Some of these people do not want the Negro to lose his grievances, because they do not want to lose their jobs."
Ants take slaves.