Deuteronomy 20:2

Priest. Eleazar, the high priest, acted in this capacity in the war against Madian, and sounded the trumpet, as it was not beneath his dignity. Many priests always attended the army, (Calmet) the captain of whom (Haydock) first made the declarations (ver. 5, 6, 7,) to the whole army; and these were repeated by the inferior priests at the head of each company, when the army was set in array. So were also the promises of protection, (ver. 3, 4,) when all were ready for battle. The Rabbins assert, that the option was granted only in those wars which were undertaken without the express command of God, and that officers were placed in the rear with hatchets or scythes, to cut the legs of those who attempted to flee. (Grotius; &c.) --- But this seems to be an invention of their own, and Moses makes no distinction between voluntary wars and those of precept. These regulations were, no doubt, observed, through the sacred historians do not mention the particulars. (Calmet) See 1 Machabees iii. 56.