Order Description

What is a legitimate authority? (use Just War theory perhaps) – is there an authority that has absolute power?
To what extent do soldiers have a duty to investigate what orders they are carrying out

Include McMahan’s theories to backup (McMahan: believes that soldiers have a duty to take an intelligent interest in politics. It could be said that the duty is even greater than the duty of ordinary citizens because soldiers are asked to carry out horrible orders (killing, torturing, and so on).