1)
Why does the Torah describe Amon as 'strong'? Were they stronger than Yisrael?
1.
Rashi and Targum Yonasan: They were strong due to Divine protection, inasmuch as Hashem had warned Yisrael 1 not to harass them (since the time of their destruction had not yet arrived ? Targum Yonasan).
2.
Da'as Zekenim and Hadar Zekenim: Sichon conquered Amon only up to the river Yabok, since it was a strong border. (Therefore, Yisrael could take only until there.)
1
Rashi: See Devarim, 2:19.
