During a Fox News interview, Trump said that the problem with the US’ handling of the war against ISIS was that “we’re fighting a very politically correct war,” and so “the other thing is with the terrorists, you have to take out their families.”

Any intentional killing of civilian non-combatants is a war crime, though Trump previously asserted that the military wouldn’t refuse any orders from him.

Trump has also said he would reimpose torture techniques, threatened to target enemy cultural sites, and pardoned US soldiers convicted of war crimes.

Time – Donald Trump Says He’d ‘Take Out’ Terrorists’ Families
The Hill – Trump on terrorists: You have to take out their families
Politifact – Geneva Conventions bar Donald Trump’s idea of killing terrorists’ families, as Rand Paul says