What is considered "ke'Karavchem el ha'Milchamah"?
Rashi: Once the army has left the borders of Eretz Yisrael.
Which Kohen is the Torah referring to?
Why does the Torah insert the (otherwise superfluous) words "Venigash ha'Kohen"?
Yerushalmi Sotah, 7:1: To teach us via a Gezeirah Shavah "Venigash ha'Kohen" "u'Moshe Nigash" from Matan Torah, Yisro Sh'mos, 20:21, 1 that the Kohen had to speak to the troops specifically in Lashon ha'Kodesh.
Oznayim la'Torah (citing Bereishis Rabah - at the beginning of Vayigash Bereishis): 'Hagashah' has connotations of Milchamah, Piyus (consolation) and Tefilah. Here too, the Kohen Gadol came to prepare the army for battle, to appease the soldiers who were about to go into battle - and those who were afraid of the sins that they had commited, and although his words were spoken to the soldiers, they were also directed at Hashem in the form of a Tefilah. 2