Part one: Ready to strike any time, anywhere - al-Qa'ida's murderous mission

The Enemy

If anything is a signature of al-Qa'ida, it is the staging of simultaneous attacks. From the September 2001 "spectacular" which targeted both towers of the World Trade Centre in New York as well as the Pentagon in Washington, to the abortive attempt a year ago to hit Israeli tourists in the air above Kenya at the same time as others were dying on the ground, the movement created by Osama bin Laden has sought to sow confusion and fear through the use of double strikes.

Istanbul added a terrifying new twist to its modus operandi: in the midst of devastation and distress, al-Qa'ida, through its Turkish allies, returned within the space of a week to stage a second pair of attacks. Thursday's suicide bombings of the British consulate and the local branch of the British-based bank HSBC were not only all the more unexpected for coming just five days after the previous Saturday's bombs at two synagogues in the same city, they were timed with chilling precision to coincide with the high point of President George Bush's state visit to Britain. They sent a powerful message to three countries at once: al-Qa'ida is still alive and still venomous.

That is one of the few clear statements one can make about the "war on terrorism". "Unlike wars against a conventional enemy, al-Qa'ida has no territory to occupy, no army to surrender and no flags or statues to tear down," Kevin Rosser, a Middle East analyst for Control Risks, writes in the consultancy's risk assessment for 2004. "It is a nebulous entity, with operatives and sympathisers scattered in as many as 60 different countries."

Terrorism experts disagree on whether the 2001 invasion of Afghanistan, which ousted the Taliban regime and scattered the al-Qa'ida leadership and its followers, has decapitated the movement. Some argue that while Mr bin Laden and his chief lieutenant, Ayman al-Zawahiri, remain at large, they will continue to have an influence, though there is no dispute that the US and its allies have struck some serious blows at the network. In particular, the capture in Pakistan last March of Khalid Sheikh Mohammed, al-Qa'ida's top operational planner, removed a crucial element of co-ordination.

"In October 2001 al-Qa'ida's inner core numbered about 4,000," said Rohan Gunaratna of the Institute of Defence and Strategic Studies in Singapore and the author of Inside al-Qaida: Global Network of Terror. "Today their strength is about 1,000, but that has not removed their ability to strike. They compensate for their comparative lack of operational capability by working with the groups they armed, trained and financed in the past, especially in Afghanistan. Al-Qa'ida has been weakened, but it has not been operationally defeated."

Since September 2001 al-Qa'ida has not struck successfully in the West, where it is actively hunted, public vigilance is high and there is unprecedented co-operation among intelligence and police agencies. But Dr Gunaratna said: "Though the network's capacity to attack in Western Europe and the US has diminished, it has not lost its interest in doing so. Any complacency will be punished."

In the meantime al-Qa'ida has reverted to what some call "franchise terrorism": using regional partnerships to hit at Western interests in the "global south" from where it draws its recruits. This is where it began in 1998, when it attacked the US embassies in Nairobi and Dar es Salaam. And as American targets abroad are better protected, it is switching its attention to Washington's close allies, with considerable success. It has killed German tourists in Tunisia, French naval technicians in Karachi, Australians in Bali - and Britons in Istanbul.

When diplomatic, military and government institutions become more difficult to attack, even in the less stable parts of the world, al-Qa'ida can take its pick of softer - mainly commercial - targets which cannot all be protected. The rhetoric of a "war against terror" creates expectations that sooner or later it will end in victory, but it is impossible to foresee an end to a campaign against an adversary which has no negotiable demands, just a utopian vision of a medieval form of Islam ruling the world. "In many respects al-Qa'ida's attacks are an end in themselves," said Josh Mandel, another Control Risks analyst.

If we are at war with al-Qa'ida, hunting down its operatives and preventing their attacks is simply the tactical part. The longer-term strategic aim should be to deprive the movement of recruits, but that will require several things to happen, none of them quick or easy, including the hope of peace between Israelis and Palestinians and the prospect of stability in Iraq, where a war undertaken in the name of defeating terrorism may simply end up nourishing the cause.

At the moment there is little sign that the need for a broader strategic vision is recognised in the White House, whatever attempts there may be by Downing Street and others to promote one. This lack of consensus on the ultimate aims of the "war on terror" is likely to ensure that it continues to be fought for a very long time.