There is every reason to believe that the bombs which wrought such carnage in Madrid will be followed by similar attacks on European soil if, as seems increasingly likely, al-Qaeda was responsible. Last October, Osama bin Laden singled out Spain, Britain, Italy and Poland - the American allies in Iraq - in a message broadcast by the Al-Jazeera satellite channel. He rarely threatens without at least attempting to carry out such verbal attacks. Spain was, and remains, at the top of his hit list since he belongs to the fundamentalist branch of Islam that will never forgive the Spaniards for expelling the Moors from Granada in 1492. Fervent Islamists believe it is their duty to recover all lands once ruled by Muslims. They regard any attack on a Muslim country as an attack on all Muslims, even if it is ruled by a man as evil and irreligious as Saddam Hussein. The grievances of the centuries have been compounded by the impotence of the Arab states to defeat Israel and prevent the Taleban's destruction. Further, they have suffered insults such as the senseless stationing of young American women soldiers, carrying guns and wearing shorts, on the holy soil of Saudi Arabia. These are more than sufficient reasons, in Islamic eyes, to carry the war into the heartlands of their enemies. The death and destruction their bombs inflict are, in their eyes, justifiable acts of war. There can be no doubt they will continue with their war after the success of the Madrid attack. Authorities in the countries under threat are well aware of the dangers. British Prime Minister Tony Blair's steadfast support of US President George W. Bush's Iraqi policies, allied to Britain's historic role in the Middle East, makes Britain a prime target. Stringent precautions are being taken, greater even than at the height of the IRA bombing campaign. But the bomber always has the advantage in such situations because he has the initiative. He can choose when and where to attack. The security authorities are alert to many of these attacks but, sooner or later, one will get through as it did in Madrid, despite the Spanish anti-terrorist police being on high alert for an attack by ETA, the Basque separatist group. One aspect of the Madrid bombings that is causing great concern to anti-terrorist forces is that there was none of the customary mobile telephone 'chatter', which has so often signalled the run-up to an attack. The mobiles fell silent in Madrid, except for those that detonated the bombs. Another problem for the authorities is that while the special forces of several nations are scouring the wild borders of Afghanistan and Pakistan for bin Laden - and his main core of al-Qaeda fighters has been hard hit - local branches of his movement remain able to bomb in their own areas. The Indonesian branch carried out the Bali bombings, the Turkish branch hit Istanbul, and now it seems Moroccans based in Spain attacked Madrid. This means the danger is everywhere. It has also taken on a new aspect which no European politician can ignore: bin Laden has become an important factor in the European democratic process. There is no doubt that before the Madrid bombs the conservative Popular Party, led by Jose Maria Aznar, was set fair to win Spain's general election. There is equally no doubt that the bombs led directly to the victory at the polls of the Socialist Workers' Party and its leader, Jose Luis Rodriguez Zapatero - a committed opponent of the war in Iraq. The process that led to the socialists' victory - much to their own astonishment - was complicated. The carnage reawakened widespread opposition to the war, people resented the government's immediate attempt to blame the Basque separatist group, ETA, and believed the government was withholding information. The bombing also led to a surge in voting, especially by young people - always a good thing for the socialists. The combination was unstoppable - the socialists won. Mr Zapatero became prime minister, immediately reaffirmed his pre-election pledge to bring Spain's troops home from Iraq and made his opposition to Mr Bush and Mr Blair's Middle East policies very clear. Bin Laden has thus won his first great political triumph in Europe. He has toppled a government dedicated to his defeat and seen it replaced by one which will not, at the least, be as heavily committed to Mr Bush's war on terror. There can be little doubt that the Madrid bombs were intended to affect the course of the general election, but I doubt if even bin Laden himself could have foretold the scale of his success. The old urban terror groups in Europe plotted to force governments to take such restrictive measures against them that ordinary citizens would revolt against the restrictions and overthrow the government. Bin Laden takes the opposite approach; he launches cynical, murderous attacks to destroy the government's power. And now he has succeeded. The question the politicians must now answer is: will we retaliate by stepping up the war on terror and try to crush al-Qaeda and all its branches, or do we try to make peace with the terrorists? Many careers and lives depend on the way they answer this question. Suppose Mr Bush is defeated in this year's presidential election and is replaced by a less aggressive John Kerry. That would leave Mr Blair uncomfortably exposed. Many Labour voters are fervently opposed to the war in Iraq. Which way will they vote if Britain is bombed before the next election? This is the sort of calculation being made in European capitals tonight. Christopher Dobson is a journalist who specialises in terrorism