Le Deutéronome 3:22 Halakha : Mishneh Torah, Negative Mitzvot & Sefer HaChinukh

Not to offer peace to the Ammonites and Moabites before waging war on them, as should be done to other nations, as it is said, “Thou shalt not seek their peace and prosperity (all thy days for ever)” (Deut. 23:7; Authorized English version: 23:6).

That those engaged in warfare shall not fear their enemies nor be panic-stricken by them during the battle, as it is said, “….do not tremble, nor be ye terrified because of them” (Deut. 3:22; 7:21; 20:3).

To not be terrified or to be afraid in war: That we have been prevented to not be terrified and be afraid of the enemies at the time of war and not to run away from them. Rather the obligation upon us is to strengthen ourselves against them and to stand in front of them. And about this is it stated (Deuteronomy 7:21), “You shall not be terrified in front of them.” And the prevention was repeated in another place, in its stating (Deuteronomy 3:22), “You shall not dread them.”