The London bombings surprised most people. Not Sir Ian Blair, London's most senior police commander. Only five months ago, he declared that an attack on London was inevitable.

Unfortunately, such a warning made sense. London historically has been a hotbed of support for al Qaeda. British authorities have uncovered and prevented at least six major al-Qaeda operations, including at least one planned attack on London's mass-transit facilities.

Britain's liberal policy on offering sanctuary to Islamic dissidents contributed to the gathering of so many Islamic militants that London had become "Londonistan" in the eyes of many critics. Terrorism expert Rohan Gunaratna wrote in his 2002 book, Inside Al Qaeda, that London was "al Qaeda's spiritual hub in the western world."

Many of bin Laden's statements were first publicized in London. Radical cleric Abu Qatada, sometimes described as "bin Laden's Ambassador to Europe," was based in London. His taped sermons were found in the Hamburg apartment of Mohammed Atta, the ringleader of the 9/11 terrorists.

Al Qaeda is known to have a strong network of supporters in Europe. The 9/11 attacks, in fact, were in large part carried out by an al-Qaeda cell based in Hamburg, Germany with the planning, funding and logistical support of Khalid Sheikh Mohammed, a member of Osama bin Laden's core group of terrorists.

The bombings bear many of the trademarks of al-Qaeda's handiwork: simultaneous bomb attacks designed to indiscriminately kill as many civilians as possible. The epicenter of the attacks appears to be London's financial district, a symbolic economic target similar to the World Trade Center in New York, which al Qaeda attacked on 9/11.

A similar al-Qaeda terrorist attack against a train station in Madrid, Spain in March 11, 2004 killed 191 people and became Spain's "3/11." That attack also involved bombs set to explode on trains crowded with morning commuters. The pretext for the attack was Spanish involvement in post-war peacekeeping in Iraq. The perpetrators of that attack were found to be a loosely organized cell of North African Muslim immigrants. The Madrid bombings contributed to the downfall of the Spanish government in elections held three days later. The newly elected socialist government subsequently pulled Spanish troops out of Iraq, setting a precedent that could only encourage further terrorism.

An Islamist Web site that in the past has carried statements purported to be from al Qaeda posted a statement claiming responsibility by a previously unheard-of organization, the Secret Organization of al Qaeda in Europe. This may be false claim -- the perpetrators may not actually belong to the core group of al Qaeda -- but it is likely that the terrorists involved at least were inspired by, if not formally affiliated with, the al-Qaeda terrorist network.

The Web site statement described the attack as "revenge against the British Zionist Crusader government in retaliation for the massacres Britain is committing in Iraq and Afghanistan." The statement warned other "Crusader governments," in particular those in Italy and Denmark, that they will be punished in the same way if they do not withdraw troops from Iraq and Afghanistan.

Unlike the Spanish government, though, the British government undoubtedly will stay the course in Iraq, despite the terrorist intimidation. Anticipating this, the terrorists chose to launch their attack during the G-8 summit in Gleneagles, Scotland, rather than during the recent British elections. They undoubtedly seek to drive a wedge between the U.S. and Britain on one hand and other G-8 countries less committed to fighting terrorism in Iraq and Afghanistan.

The London and Madrid 3/11 attacks have demonstrated that terrorists retain an effective support infrastructure inside key European cities. Although this network may not be capable of inflicting another spectacular 9/11 attack due to increased surveillance and counter-terrorism vigilance, it must be uprooted to prevent further 3/11-style attacks.

As the Madrid experience has shown, retreat and appeasement don't bring peace, but more violence. The terrorists must be hunted down and their support networks must be disrupted and dismantled.

James Phillips is a research fellow in Middle Eastern affairs at The Heritage Foundation (heritage.org).