After u September 2001, the George W. Bush administration declared that the United States had adopted a 'pre-emptive' military doctrine to address new threats posed by terrorists and 'rogue states' armed with nuclear, biological or chemical weapons. However, the so-called 'Bush Doctrine' met substantial international opposition when it was proposed - and even more resistance when it was applied to the case of Iraq. Subsequent events in Iraq have not made the idea any more popular. It is somewhat startling, then, that numerous states and international organisations seem now to support the call to revise long-held international understandings about when force might be used. A sizable number agree that the risk of calamitous surprise attacks, especially with nuclear, biological or chemical weapons, might justify preventive strikes or wars against terrorists or their state sponsors. Anew international norm may thus be under construction, though states continue to disagree about the agents of decision and action.