My favorite military philosopher

From THE EFFECT OF WEAPONS ON WAR:

For centuries all wounded and such unwounded prisoners as were valueless as slaves had their throats cut. No one was shocked; it was the custom. Finally, it occurred to some altruistic and thoughtful soldier that while the practice was excellent so long as he was the victor, it had it's drawbacks in the not unlikely event of his being the vanquished. The notion of humane treatment for the foe was born. Years of use sanctified the idea; it became the custom. Yet, the horrid thought pops up that help for the helpless sprang from love of ourselves, not of others; from fear of retaliation. The same situation effects the noisome idea of gassing noncombatants. It is contrary to our developed sensibilities, it will produce retaliations; it is not a safe method of war.
- Major George S. Patton, Jr., Cavalry, Cavalry Journal, November 1930

Though Patton here addresses the use of poison gas against noncombatants in warfare, I suspect he'd have made the same argument regarding the use of torture, had the question arisen.