TB Khullin 17 Rambam and Ramban disagree what soldiers may eat in a war.

The conquest of the Land of Israel by Joshua took seven years according to the rabbis’ calculation. The life and adventures of Calev ben Yefuneh is the key to this understanding. He was 85 years old when the Land of Israel was conquered. According to this he entered the land when he was 78 years old, 38 years after Moses sent the 12 spies to check out the land when he was a 40-year-old man.

The Gemara discusses the difference between how the animal was slaughtered during the 40 years of wandering and after they enter the land.

Ҥ Rabbi Yirmeya raises a dilemma according to the opinion of Rabbi Akiva, who says that the meat of stabbing was permitted in the wilderness: With regard to the limbs of the meat of stabbing that the Jewish people took with them into Eretz Yisrael, what is their halakhic status?

“The Gemara asks: When? With regard to what period does Rabbi Yirmeya raise his dilemma? If we say that the dilemma is with regard to the seven years during which they conquered the land, now, non-kosher items were permitted for them during that period, as it is written: “And it shall be, when the Lord your God shall bring you into the land that He swore to your fathers, and houses full of all good things…and you shall eat and be satisfied” (Deuteronomy 6:10–11), and Rabbi Yirmeya bar Abba says that Rav says: Cuts of pig meat [kotlei daḥazirei] that they found in the houses were permitted for them; is it necessary to say that the meat from the stabbing of a kosher animal was permitted?

“Rather, Rabbi Yirmeya’s dilemma is with regard to the period thereafter. And if you wish, say instead: Actually, his dilemma is with regard to the seven years during which they conquered the land, as perhaps when the forbidden food was permitted for them, it was specifically food from the spoils of gentiles, but their own forbidden food was not permitted.” (Sefaria.org translation)

No matter what, during the seven years a conquest the Israelites were allowed to eat trief food like bacon and shrimp!

Rambam and Ramban disagree whether a general principle can be gleaned from the Gemara. Rambam learns the general principle. In any war when the soldiers conquer an area and there’s no kosher supplies available, they may eat any forbidden food. Let me share Ramban’s commentary on Deuteronomy 6:10 where he cites Rambam and explains his disagreement.

“…And in the opinion of our Rabbis the verse further alludes [to the law] that anything found in the houses full of all ‘good’ things [that were occupied in the conquest of Canaan] may be used, even if they contained things forbidden by the Torah such as kadli of swine, or the produce of a vineyard sown with diverse seeds, or fruits of the first three years of a tree. Even regarding cisterns, it is possible that in their construction forbidden materials were used in their coat of pitch [such as forbidden wine; hence Scripture mentioned and cisterns hewn out, which thou didst not hew to indicate that they, too, were permitted to them]. Or it may be that the cisterns are mentioned figuratively, to denote the abundance of good things, thus giving them mastery over all that was found in the Land both permissible and impermissible. Thus all forbidden articles were permitted to them except [for those that were forbidden as a result of] the prohibition of idols, as he will yet clarify, thou shalt not covet the silver or the gold that is on them, nor take it unto thee etc. Therefore, he mentions here in the next section, ye shall break down their altars, to destroy the idols and their appurtenances. But whatever else was found in the Land was permissible. This permission lasted until they consumed the spoil of their enemies. And some Rabbis say that this permission applied [only] to the seven years of [the] conquest [of the Land], and so it appears in the Gemara, in the first chapter of Tractate Chullin. Now the Rabbi [Moshe ben Maimon] wrote in the Laws of the Kings and their Wars: “Armed soldiers, when they enter the border of the nations and loot from them, are permitted to eat n’veiloth and treifoth the flesh of swine and the like if they are hungry and do not find anything to eat except for these forbidden foods [i.e., only in the case of emergency are they permitted to eat these foods]. Similarly they may drink yayin nesech (wine dedicated to an idol). From tradition the Rabbis have learned: ‘And houses full of all good things — the necks of swine and the like.’” But this is not correct. For it is not because of danger to life or of hunger alone in time of war that [forbidden foods] were made permissible; rather, after they captured the large and wealthy cities and settled in them, was the spoil of their enemies permitted to them. And not to all armed soldiers [in any war throughout does this law apply as the Rabbi seems to hold], but only to [those who conquered] the Land which He swore to [give to] our fathers, as is explained in the subject before us. [Rabbi Moshe’s ruling that the dispensation applies to] yayin nesech is also incorrect, for all forbidden articles pertaining to idolatry — the idols themselves, their appurtenances, and their offerings — are all forbidden as it is said, thou shalt utterly detest it, and thou shalt utterly abhor it, for it is a doomed thing. And if the Rabbi’s intent was to permit in wartime only wine which was merely under suspicion of having been dedicated to idolatrous worship [which is a Rabbinic prohibition] — why do we need a Scriptural interpretation for this? If Scriptural prohibitions were permitted [to them], could subjects of a Rabbinic decree be forbidden?!” (Sefaria.org translation)

According to Ramban eating forbidden foods during the seven years of conquest has nothing to do with pikuakh nefesh, saving a life of a hungry soldier in the midst of a battle. It was a special gift dispensation in order to enjoy the booty of that time and place. It has nothing to do with Army regulations whatsoever.

When I was living in Springfield, Massachusetts I had the good fortune to know Kalman Chaitovsky z”l. He was the cantor at Keser Israel. I co-officiated many funerals with him. Once he told me his life story. He grew up in Poland and left with his family to come to America. They had to take a train through Nazi Germany. It was the last train that the Nazis allowed Jews to travel through their country before the war broke out. Once America entered World War II he enlisted. Being a committed observant Jew, he refused to eat Army rations because they were trief. He only ate peanut butter sandwiches three times a day during the war. He told me once he returned stateside, he never ate peanut butter again.