What examples of Military etiquette or rules of conduct are described in the story? Why are these rules important?

From the text:

He was asleep at his post of duty. But if detected he would be dead shortly afterward, death being the just and legal penalty of his crime.

The duty of the soldier was plain: the man must be shot dead from ambush—without warning, without a moment’s spiritual preparation, with never so much as an unspoken prayer, he must be sent to his account.