A soldier's chief motive is loyalty to his commander
Many motives drive a soldier. One common one has been his personal loyalty to The Leader of the forces. In the Middle Ages, the Feudal Future, a Samurai society, or other like societies, this is right and proper. A soldier's duty is to obey his leader, to seek Revenge for his death, to protect his lands and his family -- as long as the leader is the proper Blue Blood who is entitled to it by birth. (Loyalty to upstarts may get the character more grief.) In plot terms, it provides even the Riches To Rags character with supporters for his future rise In more professional forces, such as the Roman legions, the soldiers are expected to be loyal to more abstract concepts. It is treated as a problem, because it limits the higher-ups ability to freely move officers around and replace the dead or incompetent. Still it tends to appear, even if it does not go to full strength. A new officer often finds himself the Bait-and-Switch Tyrant for it. Among mercenaries, this trope has variable effects. It gives them a motive other than money, but it can lead to atrocities if the commander orders them, or just doesn't care. Usually the flip-side of A Father to His Men, and men with it also are Fire-Forged Friends with each other. A military form of Undying Loyalty. Compare the Old Retainer. This trope is seldom concerned with any form of propiety except the necessity of protecting the superior.