The Permitted Fruit: A Captive Woman

Eshet Yefat Toar is one of the topics in the Torah that speaks more than any other of free will, determinism, and a person's ability to withstand temptation.  

A soldier who went to a volitional war was allowed to sleep with a female captive who he found attractive. There is a heated debate between Rashi and Tosfot about whether or not the soldier was allowed already on the battlefield to sleep with the woman. The Tosfot says "yes," Rashi, "no," but even more than interesting than the Ramban who says that the woman is given a month to cry for her parents because it's inappropriate for a Jewish man to sleep with a non-Jewish woman who is still tainted by, and immersed in idol worship, the Even Ezra is particularly surprising. 

He doesn't say explicitly at what point the Jewish soldier can have relations with the woman, but he takes a particularly humane approach. He says that the woman is given a month to cry for her parents because she is saddened that they too can't become Jewish (presumably, they're dead), and thus, that month, writes the Even Ezra is a mourning period; the same way a Jewish woman needs to mourn for her parents, this captive will soon become Jewish, and similar to any other woman born Jewish, she has an obligation to sit shiva, or sit in avel, and feel the loss of her parents and show them the proper due and respect.