Halakhah sa Deuteronomio 21:11: Mishneh Torah, Kings and Wars, Mishneh Torah, Positive Mitzvot & Sefer HaChinukh

Similarly, one may have sexual intercourse with a non-Jewish woman if his lust gets the better of him. But, he must not just have intercourse with her and go. Rather, he must take her home, as it says, “and when you see a Woman of Beauty among the captives” (Deut. 21:11). He may not have intercourse with her a second time until he marries her.

The Woman of Beauty is permitted only in the hour of capture, as it says, “and you see her among the captives” (Deut. 21:11). This is applicable whether or not she is a virgin. Even if she is a married woman this Law applies since there is no concept of forbidden interpersonal relationships among the non-Jews⁷⁰Actually, since they do not have the concept of “sanctification”, the Rambam is referring to relations between Jews and non-Jews. However, as far as relations between non-Jews and non-Jews are concerned, they are considered married and the prohibition against adultery is applicable for them.. From “And you desire her” (ibid.) we learn - even if she is not pretty; from “unto her” (ibid.) we learn - and not with her friend, for you may not have relations with a second one; from “and you shall take her as a wife” (ibid.) we learn - you may not take two and have relations with one and leave the other for your father or brother. From where do we know that we do not coerce her (to have relations) during the war⁷¹Probably, “out in the open”., as it says, “and you shall bring her home” (Deut. 21:12). He must take her back to the city⁷²Lit., an open place. and only then he may have relations with her.

To deal with a beautiful woman taken captive in war, in the manner prescribed in the Torah, as it is said, “(when thou goest forth to war) …. and seest amongst the captives a beautiful woman….” (Deut. 21:10-14).