Essentially it is entirely based upon the rules of engagement which vary from mission to mission and sometimes evolve daily. ROE's generally boil down to the political climate of the operation and the misdion intent.
Soldiers are often very small cogs in very large machines, that can have positive or negative effect on a global scale through their actions.
And sometimes, the dogs of war are let slip and we do our jobs as designed, ref: Iraq and Afghanistan.
Everything is mission specific.