Deuteronomy 20:3 Halakhah

וְאָמַ֤ר אֲלֵהֶם֙ שְׁמַ֣ע יִשְׂרָאֵ֔ל אַתֶּ֨ם קְרֵבִ֥ים הַיּ֛וֹם לַמִּלְחָמָ֖ה עַל־אֹיְבֵיכֶ֑ם אַל־יֵרַ֣ךְ לְבַבְכֶ֗ם אַל־תִּֽירְא֧וּ וְאַֽל־תַּחְפְּז֛וּ וְאַל־תַּֽעַרְצ֖וּ מִפְּנֵיהֶֽם׃

and shall say unto them: ‘Hear, O Israel, ye draw nigh this day unto battle against your enemies; let not your heart faint; fear not, nor be alarmed, neither be ye affrighted at them;

Read halakhic rulings (Jewish law) on Deuteronomy 20:3: and classical halakhic sources.