Fighting spirit is a force multiplier! As part of the preparations for combat,
the fighting spirit must be strengthened.
תָּנוּ רַבָּנַן: אַרְבָּעָה צְרִיכִין חִזּוּק, וְאֵלּוּ הֵן: תּוֹרָה, וּמַעֲשִׂים טוֹבִים, תְּפִלָּה, וְדֶרֶךְ אֶרֶץ.
Connected to the emphasis on the need to bolster one’s effort in prayer,
the Gemara notes that the Sages taught in a baraita:
Four things require bolstering, constant effort to improve, and they are:
Torah, good deeds, prayer, and occupation.
...From where is it derived that occupation requires bolstering?
As it is stated: “Be strong and we will be strong for the sake of our nation and for the cities of our G-d”
Rashi explains the need for 'reinforcement' in the military context:
"That a person should always strengthen them with all his might.
That is: a man of war needs to strengthen his fighting spirit constantly and not as a one-time thing.
The Rosh Yeshiva in a pep talk to an elite unit.