If I have to reduce all of the laws of war into a single...

If I have to reduce all of the laws of war into a single sentence, it is this. You divide the world into two, combatants and noncombatants. You can attack deliberately combatants, but not deliberately noncombatants. Israel acts that way. It attacks combatants and accidentally kills noncombatants. But in the case of the terrorists, it's the exact opposite. They deliberately attack combatants - noncombatants, civilians, deliberately.