In September 2002, the Bush administration unveiled its National Security Strategy, offering its blueprint for how the United States would pursue its global interests in the post-11 September 2001 world. Although the strategy was far ranging, much of the attention at home and abroad focused on what appeared to be a novel, broad assertion of the right to use force to prevent latent threats from emerging, particularly threats associated with terrorism and nuclear, biological or chemical weapons. For the Bush administration, this was no abstract principle – but rather the underpinning of its decision, just six months later, to launch an invasion of Iraq in response to what the administration claimed was a vigorous nuclear, biological and chemical weapons programme that might someday be used against the United States, or put in the hands of terrorist enemies of the United States.
The administration justified the need for an expansive doctrine of preventive force by pointing to the risks of inaction in a world full of increasing and shadowy dangers:
The United States has long maintained the option of preemptive actions to counter a sufficient threat to our national security. The greater the threat, the greater is the risk of inaction – and the more compelling the case for taking anticipatory action to defend ourselves, even if uncertainty remains as to the time and place of the enemy's attack. To forestall or prevent such hostile acts by our adversaries, the United States will, if necessary, act preemptively.
Its critics immediately denounced the doctrine as dangerous and destabilising. Although the decision to articulate a formal doctrine of preventive force was a departure, the use of preventive force – and the debates over its legality and wisdom – predates the Bush administration's post-11 September strategy. A careful examination of the history, rationale, costs and benefits of using preventive force suggests that, while rare, preventive force has a legitimate role to play in tackling some of the most dangerous security problems facing the United States and the wider international community.