All is Fair in Love and War: "The concept behind the phrase is that some areas of life are so important and overwhelming that you cannot blame someone for acting in their own best interest. For war, this implies that spies, torture, lying, backstabbing, making deals with enemies, selling out allies, bombing civilians, wounding instead of killing, and so on are "fair game" in the sense that by taking these options off of the table you are only hurting yourself: Your opponent has no reason to comply to your moral standards."