It has become commonplace to say the world changed forever on September 11. In fact, it changed way before then. Since the end of the Cold War, the main threat to Western security has come from people who take affront at the very notion of civilized values and the existence of democracy.
What the gruesome attacks on the twin towers and on the Pentagon demonstrated was not some new intent on their part to destroy everything and everyone we hold dear but a new capacity to carry it out.
That is why the United States and United Kingdom must act together to root out and destroy the apparatus of terror whenever and wherever we find it.
Groups like al Qaeda and fanatics such as Osama bin Laden need bases to operate from, they need financial and logistical support networks. Above all they need regimes that will protect them, actively encourage them or else turn a blind eye to their activities.
There used to be a symbiotic relationship between the terrorist organizations that conducted foreign policy for rogue states at arms length and the safe haven these states provided in return.
That relationship hinged on the belief that the West would never move against such nations unless they carried out acts of terror directly. The clarity of purpose shown by America and allies like Britain since September 11 has completely undermined this equation.
The Taliban are being made to pay the ultimate price for their complicity in mass murder. But we should remember that the threat they represent will not disappear with the fall of Kandahar or the capture of bin Laden. This problem did not begin in Afghanistan, and it will not end there.
The war against terrorism will never be won while countries continue to harbor terrorist groups and retain weapons of mass destruction or the capability of developing them.
That is why President Bush is absolutely right to demand that Iraq allows the weapons inspectors back in. We have to send Saddam Hussein an unambiguous message. He can either take steps to rejoin the rest of the civilized world or face the consequences.
I have backed the British government in supporting America, and I believe that Britain is once again in the forefront of ensuring that the coalition remains in full support of the United States.
The civilized world has to recognize that traditional methods of arms control by themselves are simply inadequate to deal with the problems posed by weapons of mass destruction. Those who possess them and the mentality to deploy them are also the least likely to abide by the niceties of international treaties.
So we must prepare ourselves as Secretary of Defense Donald Rumsfeld has said “for the long haul.” And we must prepare for a greater range of threats to our security than we have ever faced before, from the suicide bomber to the hostile countries armed with biological, chemical or even nuclear weapons.
Since September 11, some people have argued that, by using passenger jets as bombs, bin Laden has highlighted the futility of ballistic missile defense. I say only this to them: If he was prepared to kill hundreds of innocent civilians in order to kill thousands more, does anyone seriously believe he would not have used a nuclear device if it had been at his disposal?
From my days in the army I know that the presence of one threat does not prove the absence of another.
That is why we back wholeheartedly the Bush administration’s plans to develop and deploy an effective ballistic missile defense shield for the security of the United States and her allies. September 11 makes that work more urgent, not less.
The more uncertain the times, the surer our response must be.
Rogue states must know that the days when they could harbor terrorists or develop weapons of mass destruction with impunity are over. The international community will work to bring these nations back within the fold, but if they refuse to co-operate they will face resolute action.
The terrorists themselves must know that we will hunt them down, cut off their finances, break their links with organized crime and bring them to justice wherever they are.
And our own people must know that we will be vigilant on all fronts to protect the very openness of our societies that the terrorists would seek to destroy.
The atrocities of September 11 were not simply attacks on the territory of the United States, they were assaults on what Britain and America stand for. That is why we stand together in the defense of freedom, and it is why we must continue to stand together.
Concluding the mission in Afghanistan, to paraphrase Winston Churchill, is only the end of the beginning of the war against terrorism.
Now is not the time to walk away with the job half done.
Iain Duncan-Smith is the leader of the British Conservative Party.