After the 2004 Madrid bombings, the 2005 London attacks, and the myriad terrorist plots thwarted over the last few years, commentators and policymakers on both sides of the Atlantic have come to the realization that Europe faces an enormous challenge from terrorism of Islamist inspiration. Yet terrorism is only the tip of the iceberg, the most visible manifestation of a larger problem. Europe faces today a tripartite threat from radical Islam, of which the terrorist is only the most immediate and evident, but not necessarily the most dangerous one.

The European Islamist Pyramid

This tripartite threat can be visualized as a pyramid. At the top of it are the violent jihadists, a few thousand individuals scattered throughout the continent who openly challenge the societies they live in, and are willing to spill blood to achieve their goals. Below them are what can be defined "peaceful revolutionaries," groups and networks that openly express their opposition to any system of government that does not strictly conform to shari'a (Islamic law), yet do not, at least openly, directly resort to violent means to further their agenda. Finally, the base, the largest section of the pyramid, is occupied by groups that publicly purport to support democracy and the integration of Muslim communities within the European mainstream, but quietly work to radicalize Europe's Muslim population.

Each of these aspects of radical Islam has a different presence, structure and modus operandi. Each, consequently, presents a different kind of challenge to European policymakers and intelligence agencies. And while Europeans are finally paying attention to the jihadist threat and have devised solutions to contain it, there is only a limited understanding of the other two threats.

The Jihadists

Individuals that espouse the most militant interpretation of Islam began to establish a presence in Europe in the mid-1980s. Their numbers were reinforced at the end of the decade and during the first years of the 1990s, as small groups of so-called Afghan Arabs and other committed jihadists who escaped prosecution (or worse) in the Middle East and North Africa settled in Europe. Exploiting the freedoms of the West, these violent Islamists continued to support their groups' activities in their countries of origin through propaganda, fundraising, and recruitment. Europe constituted the ideal logistical base for groups such as the Egyptian Gamaa Islamiya or the Algerian GIA (and then the GSPC), which established extensive networks throughout the continent.

By the second half of the 1990s these groups and networks began to gravitate toward the orbit of al-Qaeda, embracing its message of global jihad. It was in places such as Bosnia, Chechnya, and, of course, Afghanistan, that jihadist groups from various countries made contact and decided to join forces, fighting not only against their traditional enemies (regimes in the Muslim world), but also against "the far enemy," i.e. the West.

A key role in this cross-pollination of ideas and methods among jihadist groups was played by some of Europe's most radical mosques, such as London's Finsbury Park, Milan's Islamic Cultural Institute, Vienna's Sahaba, or Hamburg's al-Quds, which became popular meeting points for radicals from all countries. These networks that had long operated independently in Europe soon became franchises for al-Qaeda on the continent, significantly contributing men, funds, and logistics to the group's growth.

Over the last few years, there has been a generational change in jihadist networks. Most of today's jihadists, particularly in northern European countries, are second-generation Muslim immigrants in Europe (with a small but significant number of converts).

Today we can visualize the reality of jihadist networks in Europe as a continuum. At one extreme, we find homegrown groups: small clusters of mostly European-born radicals with no ties to external groups that act in absolute operational independence. At the opposite side of the spectrum, we see compartmentalized cells contained in a well-structured network and subjected to a hierarchical structure, as was the model of jihadist groups operating in Europe in the 1990s.

In between these two extremes there is a whole spectrum of realities, positioned according to the level of autonomy of the group. The most recurring model seems to be that of the July 7, 2005, London bombers: a small group of young men, most of whom were born and raised in Europe, who know each other either from the mosque or from the neighborhood, and who become radicalized in Europe. Only a few of these locally groomed jihadists travel abroad to gain from various al-Qaeda affiliate groups the necessary bomb-making expertise that will make the group jump from an amateurish cluster of friends to a full-fledged terrorist cell.

The challenge posed by jihadist networks, wherever they sit on the continuum, is daunting. While in the past these networks were largely focused on supporting activities taking place outside of the continent, today they consider Europe a primary target. Since 9/11, European intelligence agencies, often assisted by their American counterparts, have dismantled scores of networks and prevented dozens of terrorist attacks. Most European countries have also made significant changes to their legislation to deal more effectively with terrorism, though in some cases improvements are still needed.

Looking ahead, the task faced by European authorities is overwhelming. In Britain alone, MI5 believes that there are around 4,000 terror suspects and 200 jihadist networks spread throughout the country. Intelligence officials believe that smaller but comparable numbers of jihadists operate in other European countries, even in traditionally "quiet" areas such as Scandinavia and Eastern Europe.

The Peaceful Revolutionaries

A complete rejection of Western values and proclaimed desire to establish an Islamic state (Caliphate) worldwide are the characteristics not only of jihadist groups, but also of several seemingly non-violent organizations operating in Europe. The most organized among these "peaceful revolutionary" movements is Hizb-ut-Tahrir (HT, or Party of Liberation), which has established a presence in most European countries. HT's worldview is simple: all the solutions to man's political, economic, cultural, and social problems are to be found in Islam, and the only way for humanity to achieve justice is to abandon any man-made system (including democracy) and establish a Caliphate encompassing not simply today's Muslim world, but every non-Muslim state, too.

HT's message is spread through an unrelenting propaganda effort. This includes websites and publications in various European languages, leaflets in Muslim neighborhoods and in front of mainstream mosques, and even videos on YouTube. HT conferences, attended by thousands of sympathizers, are regularly held in the United Kingdom, Denmark, Austria, and Germany. HT is so strong in Europe that, in what is a seemingly counterintuitive but telling move, several of its members have traveled to the Middle East to spread the organization's message and re-Islamize Middle Eastern masses.

HT does not simply appeal to the disaffected masses of unassimilated European Muslims. Members of HT tend to be highly educated young professionals who are second-generation Muslim immigrants in Europe. Their ranks are buttressed further by a small cadre of converts.

HT's rhetoric is sophisticated and skillfully tailored to the ears of Western Muslims. Moreover, it generally stops short of expressly advocating violence, in order to avoid scrutiny by authorities. HT states that Islam is under attack, that Muslims have a duty to defend their fellow Muslims worldwide, and that they must establish the Caliphate in order to mount this defense. However, HT stops short of specifying how Muslims should do so.

While HT does not openly endorse violence it provides powerful ideological tools to radicalize Muslims. The jump from embracing HT's worldview to committing violent acts in order to further its goals is a short one. For this reason, HT is often identified as a "conveyor belt" to terrorism. Moreover, while the organization itself has never been directly linked to terrorism, some European HT members have.

HT continues to frustrate many European governments. Germany banned HT in 2002 for being anti-Semitic, but the group continues to operate under different names. Similarly, after the London bombings, the British government attempted to ban HT, but desisted after realizing that the lack of direct links to terrorism would pose legal challenges. Other European countries debate whether HT's activities should be banned or whether they should be safeguarded by freedom of speech.

In recent months there have been indications that HT preaches violence in small gatherings, or where it believes the media or intelligence agencies are not monitoring its activities. Shiraz Maher, a former HT regional director in England, who has left the group and produced a documentary for BBC about it, is clear in his belief that HT does not eschew violence. "Hizb ut-Tahrir despises democracy and believes shari'a law must be imposed over the whole world," says Maher, "by force if necessary."

Maajid Nawaz, another former senior HT member, asserts that "they [HT] are prepared to, once they've established the [Islamic] state, to fight other countries and to kill people in the pursuit of unifying this state into one state." Nawaz also acknowledges the disruptive impact that his former group's teachings have had on society at large: "I think that what I taught has not only damaged British society and British Muslim relations and damaged the position of Muslims in this society as British citizens, I think it's damaged the world."

Islamization by Penetrating the System

At the bottom of the pyramid is the numerically most significant component of political Islam in Europe: the Muslim Brotherhood and other revivalist movements such as the Pakistani Jamaat-e-Islami or the Turkish Milli G?r?. Over the last half-century, these movements have established offshoots in numerous European countries, thanks to their activism and foreign funding. Revivalist organizations such the Muslim Council of Britain, the Union of Islamic Organizations of France, or the Islamic Society of Germany have become the de facto representatives of the Muslim communities of their countries. They control a large number of mosques and interact with government institutions as preferential partners.

When dealing with the media and governments, these organizations present a moderate fa?ade, publicly supporting integration and democracy. Yet in their mosques, revivalist organizations espouse a diametrically different rhetoric, still embracing the zealous ideology of the organizations of their origins. Their aim is the radicalization of European Muslim communities and the creation of Muslim separatists who seek separate social spaces (from schools to swimming pools) and separate jurisdiction.

While they do not officially advocate the use of violence in the West (although they do so in Iraq and the Palestinian territories), it can be argued that these revivalist groups pose a challenge more insidious than that of other Islamists who openly challenge Western governments and values. Thanks to their public words of moderation, they often manage to establish preferential relationships with European elites. In some cases, they are even seen as partners in European governments' fight against radicalization. The legitimization and power they acquire through these government endorsements allow them to augment their status within the Muslim community and, hence, their ability to radicalize it.

Revivalist organizations concentrate their efforts in radicalizing European Muslim populations, while appeasing and penetrating the official governing system. Operating within the legal framework, and often with the support of European governments, their activities create the foundations on which other, more radical groups build. They represent the base of the pyramid and a problem that Europeans have been unable to address.

Europe's Challenge

Each section of the Islamist pyramid poses a different kind of challenge to Europe's security and way of life. Europeans must recognize each as such and find the appropriate legal and political tools to address them.