Дварим 20:4 Комментарий: Rashi, Or HaChaim, Rabbeinu Bahya & Tur HaArokh

כי ה׳ אלהיכם וגו׳ FOR THE LORD YOUR GOD [IS HE WHO GOETH WITH YOU] — They come to war relying on the conquering strength of human beings (lit., flesh and blood) but you come relying on the strength of the Omnipresent God! The Philistines once came to war relying on the strength of Goliath — what was his end? He fell and they fell with him (Sotah 42a).

להלחם לכם..להושיע אתכם, "to do battle for you with your enemies and to save you." The meaning of להלחם is to destroy your enemies, whereas the additional להושיע אתכם means to ensure that not one of you becomes a casualty of war. This last point is always the essence of the miracle by means of which we know that G'd fights on our side. This may be the reason that at the beginning of the verse the Torah mentions ה׳ אלוקיכם emphasising that both the attribute of Mercy and the attribute of Justice are involved here. The attribute of Mercy expresses itself by saving the Israelites, the attribute of Justice by destroying its adversaries. Had it not been for the Torah wanting to emphasise this it only had to write כי אלוקיכם הולך.

להושיע אתכם, “to save you.” This promise refers to total salvation, i.e. that the Israelites would not suffer casualties in their war of conquest against the seven Canaanite nations. It will be just like the punitive campaign against Midian when not a single Israelite soldier was even hurt (Numbers 31,49). It is customary that even victorious armies sustain many casualtis in battle. A war fought as a divine commandment is one when the people carrying out the commandments will prove immune. This is why Joshua was so upset when in the first battle of Ai his army sustained 36 casualties (Joshua 7,5-7). Actually, according to a commentary in Sanhedrin 44, the “36” casualties were merely a single soldier named Yair ben Menashe, who was such an outstanding person that he was considered as equivalent to 36 members of the 71-member Sanhedrin.

ההלך עמכם [FOR THE LORD THY GOD] GOETH WITH THEE — this refers to the camp of the Holy Ark (the camp that has the Holy Ark in its midst, i.e. the camp of the Levites) (Sotah 42a).