The people of Ammon were north and somewhat east of Moab. Israel, therefore, did not need to travel directly through Ammon on the way to the Promised Land. Even though they passed close to the Ammonites, and might have been tempted to wage war with them, the Lord barred them from doing so. Israel was to treat them in the same way as the Moabites.
19 et tu approcheras des enfants d'Ammon. Ne les attaque pas, et ne t'engage pas dans un combat avec eux; car je ne te donnerai rien à posséder dans le pays des enfants d'Ammon: c'est aux enfants de Lot que je l'ai donné en propriété.