Miko, most were not kidnapped, they were defeated in battle, and sold by the victor. And, uh, I hate to tell you, but the primary enslavor's were black, just like the slaves.
This does not justify slavery, but it does present it in it's true light, which in that era was not unkown in ANY region of the world, Europe included.
Blacks enslaved Blacks, repeat after me(just as they currently do in our more enlighted, modern world).