I think the most important thing leaders need is to have good character with strong values. Warfare gets real messy sometimes and you may have to make morally difficult decisions in time constrained environments. Your subordinates will often execute these orders on your behalf and it is imperative that you maintain their trust and confidence in your ability to weigh mission requirements against their physical and mental well being. Do you shoot the teenager holding the weapon? Was that a VBIED or just a panicked taxi driver? Do you drop an air strike into the population center to suppress the mortar operating there? There are no easy answers to any of these questions and you won't have a lot of time to weigh your options. It's easier to do this if you, and your people, do your best to keep your moral compass pointed north and hold on to your values as the world deteriorates around you. This will also help your subordinates work through the aftermath of complicated scenarios and process any associated guilt.