The statement by Tony Blair on Wednesday that British troop numbers in Iraq will shortly be scaled back by 1,600 men may have led some to conclude that the country’s commitments overseas — military and diplomatic — were in the process of being dismantled. Any such belief, ignorant as it was, was corrected last night when Des Browne, the Defence Secretary, confirmed that additional forces would be dispatched in due course to Afghanistan. Meanwhile, senior political representatives of the five permanent members of the UN Security Council plus Germany are expected to meet in London to discuss the steps that should be taken in the light of Iran’s continuing nuclear development .

The notion, therefore, that the foreign policy difficulties facing the major democracies of the world are all related to the intervention in Iraq and its aftermath is fallacious. Iraq is but part of a complex and interrelated picture which involves extremism and fratricide, but also includes Iran’s expansionist activities, the revival of the Taleban, Syria’s aggression towards Lebanon, the Israeli-Palestinian conflict and the danger that is likely to come from the turmoil in Somalia.

The potential damage from what is as much an emerging “arc of anarchy” as an “arc of extremism” is enormous. It is not one which Britain as a leading player in international affairs could ignore. These are events that will consume as much of the next Prime Minister’s time as the present one’s — whether he, his political party, opposition parties, and parts of the press or the public want it or not.

In Afghanistan, ministers are right to assert that they require reinforcements on the ground before a spring offensive can be launched by the Taleban. Britain has been in the vanguard of these operations and has had considerable success.

Extra men will plainly help but other nations also need to deepen their commitment. Nato has 33,000 soldiers in Afghanistan. That is an impressive force but they have not been mobilised as effectively as they could have been. As Kim Howells, the Foreign Office minister, said with commendable candour this week, some European countries’ helicopters “might as well be parked up in leading European airports for the amount of good that they are doing in Afghanistan”. Europe as a whole has to appreciate the need for it to address this threat to international order.

Much the same is true of Iran. The collective position of many states appears to be that they do not want Tehran to develop nuclear weapons, do not want to impose robust sanctions against it and do not want to raise even the theoretical idea of any military action whatsover. This is an utterly unsustainable set of propositions. If the EU and Russia cannot summon serious resolve on this issue then an awful choice will surely come between bombing Iran or letting it acquire the Bomb.

There is a middle course available. It involves imposing sanctions that have a real impact on Iran’s leadership, retaining the possibility of a military response if all else fails and reaching out as much as possible to the people of Iran. The recent willingness of Russia to suspend its assistance to Iran’s civil nuclear drive to protest that it has not been paid on time implies that Moscow might be prepared to squeeze Tehran if its leadership, notably President Ahmadinejad, does not choose to behave more responsibly.

Some want these challenges met without Britain’s involvement. This is neither noble nor realistic. Progress in Afghanistan and on Iran is possible. It will not be made by wishing these problems away.