Even though we said in Mitzvah #505 that the kohanim, as the spiritual leaders of the nation, were to live lives dedicated to peace, there is one area in which they were participants in battle. The kohein designated “meshuach milchama” (anointed for war) was designated to inspire the troops prior to battle.
The kohein chosen for this task was anointed with the special oil that we discussed earlier, way back in Mitzvah #107. He was to recite the text given in Deuteronomy 20:5-7, as well as giving his own words of encouragement. Hopefully, this “pep talk” would rouse the troops to battle fiercely on behalf of God and the nation.
The reason for this mitzvah is simple enough: the soldiers need encouragement, and who better to provide it than one of their spiritual leaders? The kohein also dismissed any soldiers who were too preoccupied or fearful to do their jobs since, as we mentioned in the previous mitzvah, such unfocused soldiers could bring down the entire army. Legitimate reasons to be excused included betrothing a wife but not yet consummating the marriage, building a house and not yet living in it, and planting a vineyard but not yet harvesting it. People in such circumstances worry about being killed and another man taking their place. (Such people were only excused in optional wars, not obligatory wars.)
This mitzvah applies at a time when the Jews reside on their land. It is discussed in the Talmud in tractate Sotah, starting on page 42a. It is codified in the Mishneh Torah in the seventh chapter of Hilchos Melachim. This mitzvah is #191 of the 248 positive mitzvos in the Rambam’s Sefer HaMitzvos.