According to history, slavery has been one of the oldest practice in the world. All civilizations, from primitive to advanced, practised it as a natural way of life. Wars often provided the easiest opportunity to acquire 'cheap labour' and deprivation of individual liberty.
However, it appears that a large number of enslaved people - who could belong to any race - led happy and even successful lives, and many of these bought or were given their freedom within the same societies.
But one can also imagine that there was also abuse in such practice, since humanity can be cruel as well as generous. But to claims that one race only can be viewed as being guilty of enslaving other human beings is misleading.