A War of Nerves, courtesy The Guardian, by Michael Clarke

Terrorism will never be defeated. Governments need to combine security with a sense of proportion and a commitment to political dialogue

The consequences of the Madrid atrocity will flow back and forth for some time. It underlines the vulnerability of free societies and makes London and other British cities appear all the “softer” as potential terrorist targets. George Bush and Tony Blair might feel some grim satisfaction that the Madrid bombing has brought Europe back into the “global war on terror”, but it should also force us to reflect afresh on what this is all about.

The war on terror has become a theme war, like similar “wars” on crime, poverty or drugs: fashionable and im portant, but unwinnable in the sense that wars are supposed to be won. Terrorism is a technique of violence – not a group of people – as familiar to the ancients who opposed the Pax Romana as to those who now oppose a Pax Americana. The scale and techniques of the 9/11 and Madrid attacks have certainly created new problems for societies trying to defend themselves against indiscriminate violence, but we have to understand that the phenomenon will continue and yet keep the scale of the threat in proportion to what we seek to protect.

Al-Qaida is disciplined, cohesive and selective about who it admits to its organisation. But as a “network of networks”, its inspiration spreads across 60 countries, working in various types of cell structure. Not so much a group, al-Qaida represents a movement that links itself to history, rather than a campaign that pursues politically achievable objectives. Its attack on the World Trade Centre in 1993 and the attempt to bring down 12 US aircraft over the Pacific pre-dated its presence in Afghanistan. But in Afghanistan, and for a period in Yemen and Sudan, al-Qaida trained at least 20,000 – perhaps up to 70,000 – followers. After the halcyon years with the Taliban, al-Qaida has gone back to “virtual” existence where it revels in anonymity, mystery and the fear its name generates. And it plays for the long term. As they put it, in a rare glimpse of humour: “The Americans have all the watches, but we have the time”.

Only some 3,000 al-Qaida operatives can be accounted for as arrested or killed since 9/11, and no more than a third of the leadership have been taken off the board. Al-Qaida’s “tradecraft”, as intelligence refers to it, is high and the continual mounting of operations – whether or not they succeed – is a critical objective, to promote unity, recruitment and to energise the network of networks. It is cheap and effective. The attacks on the USS Cole in 2000 and the bombings in Bali in 2002 and Casablanca last May each cost less than $70,000 to mount. The 9/11 attack required only half a million dollars and cost the world around $40bn in insured loss and another $160bn in trading losses. Leaving aside the human cost, the collective psychological impacts of such attacks create their own economic dynamic which encourages further plotting.

What can western governments do in the face of such threats? First, they must retain a sense of proportion. In his speech at the weekend, Tony Blair called all this “a new type of war” that “demands a different attitude to our own interests”. Not quite. The incidence of terror attacks in the world – about 300 a year – does not vary much. Nor do the casualty figures – about 500-600 in most years. About a third of these attacks are designed to kill, another third are symbolic – the sort of attacks in which Eta used to specialise. It is the unpredictable and indiscriminate nature of the deadly third of the attacks that creates Blair’s “new” problem. The response, as it always did, revolves around the “three Ps” – protection, penetration and political process.

Governments can take sensible measures to protect cities, travel infrastructures, government facilities and so on, though in truth their ability to do this is rightly limited by the democratic values and civil liberties they seek to safeguard. In reality, politicians talk tougher about protecting the public than they know they can be. The danger arises when they think they can do more than they actually can.

The most effective measures involve the penetration of terrorist networks so that attacks can be intercepted. This takes time, painstaking intelligence work and effective cooperation between intelligence and police services in different countries. Intelligence and police around the world now cooperate more effectively than ever. But they need to: their cooperation before 9/11 was derisory. Plots are now intercepted somewhere in Europe almost on a weekly basis. This may be comforting (or disturbing), but governments are still not sharing around enough mature – as opposed to raw – intelligence data.

Not least, governments must not neglect the third element – political process. Politicians such as José María Aznar too easily confuse this with the horror of “negotiating with terrorists”. But political dialogue is not directed at the psychopathic mentality of those who would kill indiscriminately. It is designed to divorce terrorists from their potential bases of wider support by indicating to ordinary people that the issues terrorists claim to fight for are susceptible at least to political debate. Terrorists gain greatest popular support when they can fairly claim to have no other voice.

There is no magic formula for dealing with terrorism: no one battle that wins the war, no technique that destroys the evil of it. Politicians simply have to keep their nerve, their sense of proportion, and do more of the same with greater efficiency and determination.

· Professor Michael Clarke is director of the International Policy Institute at King’s College London.