The enemies will abandon this tactic if it no longer works. Sorry about the women and the children but if worse comes to worst, the women will no longer be breeders and the children will not grow up to be terrorists. You can win on the world stage no matter what you do so you might as well kill them all and let God sort it out.
Never lose sight of the mission.
We have developed some really stupid ideas on how to run a war since WWII.