I will have to disagree with you.
Even in the current day, private military contracting companies which are basically the modern day mercenaries, do not just accept contracts from the highest bidder, the notion is completely absurd – These companies have ethics and a reputation, what if the highest bidder is ISIS.
So yes, politics are always involved, ethics play a major role in many companies decisions. The individual humans beliefs also play a huge role, if a person believes he is fighting “Evil” then he is more likely to kill, but if he feels he is doing wrong/injustice or was raised a certain way, he may find it more difficult to do something or may even desert the group or abandon the cause.
