In the early days of the second Iraq war, we heard cries of “illegal” repeatedly. The commencement of hostilities against Saddam Hussein’s “Republic of Fear” was said to violate established norms of international law; to make the United States an outlaw among nations; and to constitute a disastrous precedent. We were told that the United States had never before in its history engaged in preventive or preemptive action against a hostile foe and that, therefore, the administration of George W. Bush was sui generis in its arrogant violation of law and its besmirching of American foreign policy. These sorts of claims are subject to empirical investigation, of course, and such investigation shows them to be false. The United States has, indeed, engaged external foes in the absence of official declarations of war and in a manner that can reasonably be called preemptive if not preventive. This may or may not be a good thing, of course, but it does belie the charge of notorious originality on the part of the Bush administration at that time. Different words may be used – as, for example, the locution “anticipatory self-defense” deployed by the Kennedy administration in the days of the Cuban missile crisis – but the reality is that the United States has taken action in the past that can reasonably be called preemptive.