Reasons to and Reasons not to 

"This region hasn't been fighting against other nations for centuries, and it is relatively easy to make money here, so they have no reason to have war prisoners or people in debt to become slaves," Sauros explained. "The people you saw must be from other nations… in any case, this is another confirmation of the mess behind the curtains."

"Did they attack other places, or did they buy them?" Aion asked.

"That is hard to say… considering what you saw, I would guess that traveling to other lands would be too much of a hassle for them. Picking up a fight with them would be even more unlikely," Sauros replied. "I didn't hear them attacking other places aside from those four islands and merchant ships, so they must have traveled to waste the money they got and then bought the slaves."