There's a separate caution, get them before they get you. Ancient Israel knew there would be problems, much the same as they have now. In the old times, it was known that the people that inhabited the land would hold a grudge and attempt revenge. Therefore, the land was sterilized of it's inhabitants. Most civilization of those days practiced this foolproof method of avoiding mutiny.
Iraqi Kurdish leader vows to take Sinjar from ISIS (AP)
from the article: MKs demand the author of blood libel book be prosecuted