Rashi (this week's parsha 21:11) writes, דברה לא הרע יצר כנגד אלא תורה, "The Torah is speaking solely to counter the yetzer hara." The Beis Yisrael zt'l said that this doesn’t only refer to the parashah of תואר יפת אשת, the non-Jewish captive, captured at war (as is the simple meaning of Rashi). Instead, Rashi refers to the entire Torah, from Bereishis until Zos HaBrachah. The whole purpose of the Torah is to counter the yetzer hara. It gives us strength to stand up in battle against the yetzer hara's enticements.
Rebbe Bunim of Peshischa zt'l taught that in our generation, the hinted explanation of the pasuk is its literal pshat. The Torah applies to all generations, and since we don’t wage wars nowadays, the simple meaning of the pasuk is about the battle against the yetzer hara. The Torah promises that if we set out to fight this war, we will succeed. As it states בידך אלקיך 'ה ונתנו, you will ultimately win the war.
