This article examines what moral theories are available to justify the harming of the innocent in war. Focusing on US conduct of the war against the Taliban and al-Qaeda, the article examines how far the US is responsible for the deaths of Afghan civilians. Although US actions have been justified in terms of respect for the Just War principle of non-combatant immunity, the article shows how this principle rested uneasily with alternative moral theories of war that influenced the process of target selection. These are the realist doctrine of necessity in war and Michael Walzer’s theories of ‘supreme emergency’ and ‘war is hell’. Just War theory, realism and ‘supreme emergency’ acknowledge moral responsibility for a state’s conduct of war. But the doctrine that ‘war is hell’ seeks to transfer any responsibility for the cruelty of war to the enemy. The article argues that, whilst the Taliban and al-Qaeda are responsible for exposing Afghan civilians to US attacks, this does not absolve US political and military leaders of responsibility for their conduct of the war.