President Bush has unveiled a new national security strategy calling for the use of preemptive attacks against terrorists or rogue states that are developing weapons of mass destruction. The strategy is being debated by supporters and opponents who agree this new doctrine represents a major policy change for the United States.
For decades during the Cold War the pillars of American strategic policy were deterrence and containment, producing the grim standoff of mutual assured destruction in a nuclear conflict.
Following the collapse of the Soviet Union and last year's terrorist attacks on the United States, President Bush argues America can no longer afford to wait to be attacked before responding to threats from governments and groups who would use weapons of mass destruction to kill U.S. citizens.
"The war on terror will not be won on the defensive," he said. "We must take the battle to the enemy, disrupt his plans and confront the worst threats before they emerge."
Opponents of preemptive military action argue this change in American strategic thinking is not legal and could backfire.
For Ohio State University International Law Professor Mary Ellen O'Connell, the new doctrine of preemptive attacks is in violation of the charter that created the United Nations.
"The preemptive use of significant, unilateral, military force violates fundamental international law," she said. "The United States has historically opposed the right to use force preemptively for the soundest reasons of national security and national values. The grounds for U.S. opposition to the preemptive use of force have not changed since September 11."
But Johns Hopkins University International Law Professor Ruth Wedgwood disagrees. She says the right to use pre-emptive force is necessary because of the unconventional nature of terrorist groups and the chance they may use weapons of mass destruction (WMD).
"The signal change from September 11 is we have always presumed we would have signs of an impending attack and September 11 showed that any actor, state or non-state, can undertake asymmetric attacks of which we will have no warning whatsoever," she said. "In the case of WMD the results can be catastrophic."
Some analysts say a policy of preemption could cause any military crisis to escalate quickly by increasing pressure on both sides to act more rapidly, possibly forcing them to use weapons of mass destruction as a first option in war.
Law professor Mary Ellen O'Connell argues if the United States establishes the precedent of preemptive force, other countries will use the doctrine to attack their enemies.
"We can expect that a precedent establishing a right to use force preemptively would make the world a more dangerous place," he said. "World leaders will be able to act on their fears and not on objective evidence and that means they will be unrestrained by legal principle."
For Professor Ruth Wedgwood, the use of preemptive military strikes must occur before a country develops nuclear weapons.
Ms. Wedgwood cites North Korea's recent admission that it has a nuclear program as a reason why preemptive action is sometimes needed against governments or groups seeking weapons of mass destruction.
"Pyongyang has taught us that you can only do preemptive self-defense in a narrow window," she said. "You can not wait until he has it and say I wish I had done preemptive self-defense. Once he has the bomb - end of story. Then you live with the threat."
As part of the preemptive strike strategy, the Pentagon is reportedly working on ways to launch what it calls "no warning" raids that go beyond air strikes.
The idea is to use the least detectable elements of the armed forces, including stealth aircraft, submarines that can launch cruise missiles, and commandoes.
Defense Secretary Donald Rumsfeld says the United States can no longer wait for "absolute proof" before acting against terrorist groups or countries that may have chemical, biological or nuclear weapons.