> Your refusal to acknowledge the difference between prisoners of war
Prisoners of war? They were loot.
We should understand the institution of slavery a little better.
The economy of much of the ancient world was based on slavery. E.g. fighting wars to capture people who could then be used as slaves domestically and sold for trade. The objective of these wars was to capture this human bounty.
Especially in Africa, this was why the wars were fought as slavery was one of the pillars on which the local economies rested, and this is true as far back as we have recorded history -- which is basically the chronicles of Arab slave traders buying slaves from Africa in the 7th Century on.
The richest man in Africa - Mansa Musa - earned his great wealth via slavery, himself owning thousands of personal slaves but capturing many orders of magnitude more and then trading them for gold and other riches during the middle ages. And not only Mali, but all of Africa's great empires were slave societies based on the principles of fighting wars to capture both slaves and territory.
To try to pretend that slavery was a modern invention only practiced in order to sell slaves to Europeans in the 18th Century and later is to ignore the entire (known) economic history of Africa.