After that, let the military do it. Let them tell you how much it will cost, in money and human life, then the politicians give the order to go or not to go. If something happens that gets outside those lines you stop and re-evaluate the decision. Failure to let the military decide what level of engagment is required to meet the military objective will mean escalation, long term engagement, cost increases, etc. Politicians should not decide military tactics and military members should not seek to play political ends.
War is by design unfair.
Politicians, by nature try to be fair. In war you don't win by being fair. You win by making the other guy hurt so much he doesn't want to fight anymore. In the end, you just hope that you were doing the right thing the right way for the right reasons. Politicians set the goal, the military makes it happen.