The LORD will be furious, and instead of forgiving you, he will separate you from the other tribes. Then he will destroy you, by piling on you all the curses in The Book of God's Law, and you will be forgotten for ever.
As you attack these nations, the LORD will force them out little by little. He won't let you get rid of them all at once—if he did, there wouldn't be enough people living in the land to keep down the number of wild animals.