Sforno on Numbers 22:2/ספורנו על במדבר כ״ב:ב׳

1וירא בלק, a man who was famous as well schooled in all the martial arts. We find proof of this in Judges 11,25:הטוב טוב אתה מבלק בן צפור מלך מואב?, “do you imagine yourself to be superior to Balak son of Tzippor? Balak, in spite of his expertise, “saw” what had happened to Sichon who had refused to let the Israelites pass and had paid for this error with the loss of his life and his kingdom.