Why does the Torah see fit to mention the fact that Moshe rebuked Yisrael only after he had captured Sichon and Og?
Rashi: Otherwise, the people would say 'What has he done for us? He is incapable of taking us into the Land! So all he does is rail against us and find fault with us!' So he demonstrated his capabilities by overthrowing Sichon and Og before proceeding to rebuke them.
Seforno: He began to clarify the Torah after having attained for them 'a measure of Menuchah' (a small resting-place) in inhabited country. 1
After having spent forty years in the desert.
Why does the Torah see fir to add "Asher Yoshev be'Cheshbon" and "asher Yoshev be'Ashtaros ... "?
Ramban: Because Cheshbon originally belonged to Mo'av, and Sichon captured it from them and made it his capital, and Ashtaros belonged to the Refa'im, until Og, who was king of the Emori, captured it from them. 1
Ramban: The Torah writes this with reference to Og's origin, because at this stage, he was no longer king of the Refa'im, but of the Emori - See Ramban DH 've'Inyan Sifri'. See also below 2:10, 3:11, where he elaborates on the issue of the Refa'im.
What are the connotations of "Ashtaros"?
Rashi and Ramban (both citing the Sifri): It is synonymous with "Asht'ros Karnayim," 1 (and has connotations of a hard rock
What does "Edre'i" mean?
Rashi (citing the Sifri): "Edre'i" is the name of the kingdom (in which Ashtaros os situated). 1
Ramban: Edre'i is a town in Ashtaros.
It is not clear whether Targum Onkelos learns like Rashi or like the Ramban
Why does the Torah see fit to mention the fact that Sichon dwelt in Cheshbon, and Og, in Ashtaros?
Rashi: To teach us that, not only were Sichon and Og all but invincible, but that their towns 1 were so well-fortified that, they too, were unconquerable.
What is the connection between Og and Ashtaros?