Deuteronomy 2:24 & 25

"'Set out now and cross the Arnon Gorge. See, I have given into your hand Sihon the Amorite, king of Heshbon, and his country. Begin to take possession of it and engage him in battle. This very day I will begin to put the terror and fear of you on all the nations under heaven. They will hear reports of you and will tremble and be in anguish because of you.'" NIV translation

The Arnon Gorge is in the modern country of Jordan where the locals call it the "Grand Canyon of Jordan". At this time, it was the boundary between the land of the Ammonites and the Amorites.

We see that, before they crossed this massive gorge, God assured them that He had already gave them the land on the other side. They had already passed through lands that God had taken from others and given to their relatives. Because of that fact, they would have had a stronger faith and trust in the Lord.

We also see that their victory was going to be a testimony of God's power to the nations of the world and a reminder that, as the Creator of all things, He has the right to set the boundaries of the nations.