Sforno on Numbers 22:4/ספורנו על במדבר כ״ב:ד׳

1עתה, now that the Israelites had conquered both Sichon and Og and their respective countries.

2ילחכו הקהל את כל סביבותינו, they wanted their leaders to enlarge the area under their control in order to make their borders more secure.

3ובלק בן צפור, who was known as a hero and a military expert.

4מלך למואב בעת ההיא, in spite of these factors which should have encouraged the Moabites they did not have the heart to fight the Israelites as is clear from Judges 11,25. As to the remarks by Joshua that Balak son of Tzippor arose and fought Israel (Joshua 24,9), Joshua said this in reference to Balak hiring Bileam to curse the people of Israel as he himself pointed out in the same verse.