What is the maximum number of children who need to die before hamas(Isis) surrender?
"What is the maximum number of hostages police are allowed to kill before they negotiate with the bank robber?"
This isn't a game where the IDF has to grind kids for XP before attacking a final boss, asshole. The answer is "as few as possible, ideally zero", but the IDF has shown that they are either stupidly or maliciously indiscriminate in who they kill.