God Gave the Land of Moav to the Moabites

Perek Bet (Chapter Two) of the Book of Devarim starts with Moshe summarizing the voyages of Bnei Yisrael in the desert. As his narrative reaches the point where Bnei Yisrael come close to other nations who are blocking the way, some strange and seemingly contradictory phrases appear. At first it sounds like Bnei Yisrael turn away and avoid attack out of fear, and then the narrative states that they did not attack Moav or Edom because the Lands of Moav  and Edom were designated as such by God. What is going on here? We turn to Ramban for insight into these passages.