Hello,
A huge yashar koach for the question and for the moral sensitivity.
This is the beauty and might of the Jewish army.
As is the way of things, because of our sins we were exiled from our land, and therefore we have no organized halachic continuity in issues of military and halacha on the macroscopic level. If we, chas veshalom, copy the behavior that was appropriate in the times of the bible to now – we would of course rule that everything is permissible, and this is part of wartime spoils. However, it is prohibited to rule this way in halacha, and in no domain do we rule in this manner, rather using the tradition of the Sages and the Rishonim, who as stated – are not at play here.
In general, regarding the principles of wartime morality, I would appreciate if you read the essay “Protective Edge and Wartime Morality” on the Tzohar Ethics website, and the essay on wartime morality on the website of Yeshivat Orot Shaul. In the two essays, we did not engage with your holy question, but they provide a background to filling the gap between that which is written in the bible and us nowadays.
Indeed, the Ramban writes extremely important things regarding wartime morality. On the verse, “when the camp will go out towards your enemies and you will protect yourself from all matters of evil” (Devarim 23:10): “… and what is right in my eyes regarding this commandment, for the Torahs warns us at times when sins are found, and that which is commonplace in the practice of camps going to war is that they will eat all abominations, rob, destroy, and experience no shame even in adultery and all abhorrences, the just among men will naturally dress himself in cruelty and rage when the camp departs against the enemy, and therefore the Torah warns him ‘and you will protect yourself from all matters of evil’…”.
From his words it arises that we are obligated to protect ourselves from all evil matters, and he even demonstrates what “matters of evil” are, amongst other things writing “they will rob, destroy, and experience no shame”.
One can thus conclude from his words: anything that is necessary for the war – is ethically and halachically permissible (I want to emphasize that alongside this response, one should follow military orders, and what I write here is only from the initial viewpoint of halachic ethics), even when dealing with aspects related to it, such as water, etc. However, one should entirely abstain from using various items that aren’t directly connected to the war, as part of our obligation to protect ourselves from all matters of evil.
All the best and an extremely powerful yashar koach,
Hashem should protect you in your departure and return now and forever,
Rabbi Yuval Cherlow, Head of the Tzohar Ethics Center