Outside Iceland no nation / people isn't
residing on land taken by force from someone
else. Usually many times over.
Nothing new there. The native American fought plenty of wars among themselves to take control of land from each other. They were as brutal or perhaps even more brutal in their acquisition of land. They only had ownership of land if they could protect that ownership.
Same as it is today. The right to own land only extends as far as your ability to protect that ownership.