Preemptive war is a unilateral "first strike", in the face of an imminent armed threat. This type of war may be sanctioned under international law, but requires the nature of the threat to be credible and significant.
"A preemptive attack (or preemptive war) is waged in an attempt to repel or defeat an imminent offensive or invasion, or to gain a strategic advantage in an impending (usually unavoidable) war.
"Preemptive war is often confused with the term preventive war. While the latter is generally considered to violate international law, and to fall short of the requirements of a just war, preemptive wars are more often argued to be justified or justifiable.
"The intention with a preemptive strike is to gain the advantage of initiative and to harm the enemy at a moment of minimal protection," particularly when the enemy is vulnerable. 
In 1841, U.S. Secretary of State Daniel Webster "articulated a set of demanding criteria for acting with a 'necessity of self-defense'—in particular for a legitimate use of preemptive force. Preemption, Webster said, is justified only in response to an imminent threat; moreover, the force must be necessary for self-defense and can be deployed only after nonlethal measures and attempts to dissuade the adversary from acting had failed. Furthermore, a preemptive attack must be limited to dealing with the immediate threat and must discriminate between armed and unarmed, innocent and guilty." 
International Court of Justice
"The International Court of Justice (ICJ) spelled out exactly what no nation can legally do in light of its commitments to uphold the U.N. Charter: 'Thus it would be illegal for a state to threaten force to secure territory from another State, or to cause it to follow or not follow certain political or economic paths'," according to Ann Fagan Ginger, Executive Director of the Meiklejohn Civil Liberties Institute. 
"The prevailing view probably is that, one way or another, anticipatory self-defense is permissible but traditionally has required the existence of an imminent threat," writes Steven C. Walsh, research analyst at the Center for Defense Information. 
Preemptive war "punishes the defenseless not for what they have done or are doing but for what they might have done or could do."
—Eduardo Galeano, PaxHumana, September 2003.
Related SourceWatch Resources
- Authorization for Use of Military Force Against Iraq Resolution of 2002
- Bush doctrine
- Doctrine for Joint Nuclear Operations
- Eisenhower doctrine
- Geneva Conventions
- nuclear weapons
- Truman doctrine
- Paul W. Schroeder, "Iraq: The Case Against Preemptive War. The administration’s claim of a right to overthrow regimes it considers hostile is extraordinary – and one the world will soon find intolerable," American Conservative Magazine, undated.
- Netta C. Crawford, "The Best Defense. The problem with Bush’s 'preemptive' war doctrine," Boston Review, February/March 2003.
- Dietrich Murswiek, "The American Strategy of Preemptive War and International Law," Albert-Ludwigs-Universitat Freiberg Institute of Public Law, March 2003.
- Ann Fagan Ginger, "Preemptive War / Preventive War. Both Are Against The Law Of The United States," Meiklejohn Civil Liberties Institute, undated .
- Steven Murdoch, "Preemptive War: Is It Legal?," DCBar.org, January 2003.
- "Pre-Crime? What the Film Minority Report Can Teach Us About the Three Key Rules of Preemptive War," FindLaw's Writ, April 15, 2003.
- Russell Madden, "Self-Defense: Preemptive, Immediate, and Retaliatory" (cache file), The Laissez Faire Electronic Times, Vol 2, No 18, May 5, 2003.
- Duncan E.J. Currie, "'Preventive War' and International Law After Iraq," May 22, 2003.
- Steven C. Welsh, "Preemptive War and International Law," Center for Defense Information, December 5, 2003.
- Maggie Ledford Lawson,"The fatal legend of preemptive war. German history shows the perils of Washington's new strategy," National Catholic Reporter, February 27, 2004.
- John Hendren, "Policy OKs First Strike to Protect US," Los Angeles Times, March 19, 2005: "Two years after the U.S. invasion of Iraq, the Pentagon has formally included in key strategic plans provisions for launching preemptive strikes against nations thought to pose a threat to the United States. The doctrine also now stipulates that the U.S. will use 'active deterrence' in concert with its allies 'if we can' but could act unilaterally otherwise, Defense officials said."