In military operations involving action against terrorists, the relevance of the laws of war, often now called international humanitarian law, is problematical. The US-led 'war on terror', especially the use of armed force in Afghanistan, raises three questions. Is the law applicable to such operations? Should it be applied in situations different from what was envisaged in treaties? And are detainees 'prisoners of war'? A difficulty in applying the law is that governments usually view terrorists, like rebels in civil wars, as simply criminal. In the bombing in Afghanistan, the US has sought to observe the legal requirement of discrimination, but difficult issues are raised by the use of cluster bombs and the continued bombing after the Taliban regime's fall. As regards prisoners, US policy was ill-thought-out; and the perfectly justifiable classification of certain prisoners as 'unlawful combatants' should not mean that they are in a legal limbo. Treating the law cavalierly causes problems, especially for coalitions. The law, however imperfect, is irreplaceable.