Duty is above the letter of the law. It’s a way of calibrating what you want to do with what you’re responsible for and matching that up against how you see yourself as a person. Joe Alotto had wanted to be in the military since he was a little boy. Having become a soldier he knew his duty primarily was to hold himself accountable to the expectations his fellow soldiers had of him, and the expectations he had of himself. When you’re a soldier, though, sometimes you have to bet your life that you’re doing the right thing, and that your comrades are as well.