What is the role of fear in Jewish battle?

(3) Another interpretation (of Gen. 14:14): HE ARMED HIS TRAINED MEN. HE ARMED (yareq) means nothing but that he made them turn pale (horiq) with words, just as it is written in the Law (in Deut. 20:8): WHO IS THE ONE WHO IS AFRAID (yare) AND FAINT (rakh) OF HEART. Abraham did this: He said to them: We are going off to war. Let anyone who has transgressions on his hand and is afraid because of his actions not go off with us. When they heard that, anyone who knew in his heart that he had sinned was afraid and did not go off. So they went back, and no one was left with him (Abraham) but Eliezer alone.⁷⁴Gen. R. 44:9; Numb. R. 18:21; PRE 27; M. Pss. 110:4. In that hour the Holy One said: All have forsaken you, and no one is left except Eliezer alone. By your life I am putting within him the power of three hundred and eighteen.⁷⁵Cf. Targum Pseudo-Jonathan to Gen. 14:14. Thus it is stated (in Gen. 14:14) AND HE ARMED HIS TRAINED MEN, THE ONES BORN IN HIS HOUSE, THREE HUNDRED AND EIGHTEEN < OF THEM >. Where is it shown? The numerical value of Eliezer by gematria is three hundred and eighteen.

(15) "What man is there who is fearful and is faint-hearted" (Deut. 20:8)? Exactly so. This is one whose heart has no strength to withstand the strains of war⁶⁸He is afraid he’ll be killed in battle due to his sins.. Now, once one becomes entangled with the perplexities of war, he should trust the Hope of Israel, and He will save him in times of trouble. He should know he is doing battle for the unity of the Name. He should place his life in His Hands and neither be afraid nor alarmed. He should not think about his wife or his children. Rather, he should wipe away thoughts of them from his heart, and clear himself of everything for the war. Anyone who thinks about or contemplates (matters) during the battle and frightens himself violates a Negative Commandment, as it says, “do not be faint of heart, nor be alarmed, do not flee, and be not frightened before them” (Deut. 20:3). And not only that, but all the blood of Israel hangs around his neck. If he did not win and did not fight the battle with all his heart and soul, he is like one who spills everyone’s blood, as it says, “lest he not melt his brothers’ hearts as has his” (Deut. 20:8). It is explicitly stated in the Tradition that, “Cursed be he who does the work of G-d sluggishly, and cursed be he who keeps back his sword from blood” (Jeremiah 48:10). However, anyone who does fight with all his heart without fear, and his intentions are only to Sanctify the Name, is promised that he will not be harmed and nothing bad will happen to him. He will build an upright home in Israel, and he and his children will earn merit forever, and merit The World To Come, as it says, “certainly, G-d shall make for my master a faithful house, for the wars of G-d does my master fight and no evil will be found with you all your days…And the soul of my master will be bound with the living, with the Lord your G-d…” (I Samuel 25:28-29).

(1) It is mandatory to love and fear this Glorified and Awe-inspiring God, for it is said: "Thou shalt love the Lord thy God" (Deut. 6,5); and as it is said: "The Lord thy God thou shalt fear." (Ibid. 6, 13).

(2) But how may one discover the way to love and fear Him? When man will reflect concerning His works, and His great and wonderful creatures,¹But he must make thorough study. C. and will behold through them His wonderful, matchless and infinite wisdom, he will spontaneously be filled with love, praise and exaltation and become possessed of a great longing to know the Great Name, even as David said: "My soul thirsts for God, for the living God," (Ps. 42,2); and when he will think of all these matters,²Sifre, Deut. 6.5; Shabbat, 30–31. G. he will be taken aback in a moment and stricken with awe, and realize that he is an infinitesimal creature, humble and dark, standing with an insignificant and slight knowledge in the presence of the All Wise, as David said: "For when I see Thy heavens, the wonderful works of Thy fingers, of what use is man that Thou mayest remember him?" (Ibid. 8,4). And, in harmony with these matters, I elucidate great, general principles of the works of the Lord of the universe, so that they might serve as an opening for one who understands by which to love the Name, as some sages said on the subject of love: "Out of it thou wilt recognize the One who spoke, and the universe was called into existence."