Over the last two years, European governments and the European Union (EU) have grown increasingly alarmed by the rise of the Islamic State terrorist organization, its ability to attract European citizens to join the fighting in the Syria-Iraq region, and its use of violent extremist propaganda to inspire others. Security experts view the November 13, 2015, attacks in Paris (which killed 130 people) and the March 22, 2016, bombings in Brussels (in which 32 people died) as indications that the Islamic State's capacity to direct large-scale, coordinated attacks elsewhere in the world, especially in Europe, has increased. Many of those identified as directly responsible for the Paris and Brussels attacks reportedly fought in Syria and were connected to a "European branch" of the Islamic State. Some observers suggest that there could be many potential European recruits among the estimated 5,000 Europeans who have traveled to Syria and Iraq to join the Islamic State and other extremist groups.
At the same time, European officials remain concerned about the possibility of "lone wolf" attacks carried out by individuals who have not traveled abroad to fight but have been inspired by Islamist propaganda to commit violence at home. Although the Islamic State has claimed that the perpetrator of the July 14, 2016, truck attack in Nice, France, was its "soldier," authorities believe that the perpetrator was largely self-radicalized. At least 84 people died in this incident, including two Americans. The uptick in terrorist activity has reinforced long-standing anxieties about the integration of Muslims in Europe and the potential for radicalization among some segments of Europe's Muslim populations.
Terrorism in Europe is not new, but these incidents are the latest in a string of attacks linked to Islamist extremism and to the brand of extremism practiced by the Islamic State and its followers. Many of the recent attacks have exposed weaknesses in European domestic security, intelligence sharing, and border controls. Some perpetrators appear to have taken advantage of the Schengen system, which largely permits individuals to travel among most European countries without passport checks. For example, the suspected ringleader of the November attacks in Paris may have repeatedly traveled back and forth between Europe and Syria, despite being known to European security services. Europe's migration and refugee crisis has also heightened fears that terrorists could slip into Europe more easily. At least two of the November 2015 Paris assailants may have entered Europe through Greece in early October by posing as refugees with fake Syrian passports (authorities have yet to confirm the attackers' true identities, and EU officials caution against linking refugees with terrorism).
European governments have employed various measures to combat Islamist terrorism and the foreign fighter phenomenon, including increasing surveillance, prohibiting travel, and arresting returning fighters and terrorism recruiters. Some countries have bolstered existing counterterrorism laws, especially to ensure that individuals who travel abroad for terrorist purposes may be prosecuted (as required by U.N. Security Council Resolution 2178 of September 2014). European officials are also working to more aggressively counter radicalization and extremist propaganda, especially via the Internet and social media. Some have called on U.S. technology companies to assist these efforts by preemptively removing terrorist content from their sites.
France, which is home to Europe's largest Muslim population (about 5 million-6 million), has been at the forefront of European efforts to counter the threat posed by Islamist militants. Recent estimates indicate that up to 1,600 French nationals have traveled to fight in Syria and Iraq and roughly 2,000 people are involved in Muslim extremist cells in France. French counterterrorism policies are considered to be among the most stringent in Europe. In the past year, the government has imposed travel bans on individuals suspected of seeking terrorist training abroad, prohibited speech that encourages terrorism, and significantly enhanced the state's surveillance authorities. (For more information, see CRS Insight IN10301, France: Efforts to Counter Islamist Terrorism and the Islamic State.)
Belgium has the highest number of foreign fighters per capita of any European country (possibly as many as 550 out of a total population of roughly 11 million) and what some describe as a "well-developed underground jihadist pipeline." Authorities have prosecuted terrorist recruiters, disrupted some terrorist plots, and sought to strengthen law enforcement capabilities and better tackle extremism. Belgian officials have also pledged to "clean up Molenbeek," the Brussels district that is home to dozens of suspected Islamist militants.
Despite some progress, European officials have encountered difficulties stopping individuals from leaving for Syria and Iraq. Monitoring a growing number of potential assailants amid budgetary and personnel constraints has also been challenging, and law enforcement and intelligence capacities vary across Europe. While Belgium's counterterrorism policies have been criticized as insufficient, even France's widely praised counterterrorism apparatus has struggled to prevent attacks. Some experts suggest that increasingly tough policies in France and elsewhere targeting Muslims could further alienate them, exacerbating the potential for radicalization. Critics argue that efforts to integrate Muslims in Belgium and France have been largely unsuccessful.
Analysts assert that more must be done at the EU level. The EU has sought to enhance information sharing among national and EU authorities, strengthen external border controls, and improve counter-radicalization efforts, particularly online and in prisons. However, implementation of some initiatives has been slowed by national sovereignty concerns, law enforcement barriers to sharing sensitive information, and civil liberty protections. In April 2016, the EU adopted a long-standing and controversial proposal for the EU-wide collection of airline Passenger Name Record (PNR) data. Critics contend that it will infringe too much on privacy rights and does not go far enough in ensuring that PNR data is meaningfully shared.
President Obama strongly condemned the latest terrorist attack in Nice and reasserted U.S. support for France. The spate of terrorist attacks in Europe may raise additional questions in Congress about U.S.-led military efforts to counter the Islamic State in Syria and Iraq. The attacks also may prompt further scrutiny of law enforcement measures against terrorism and U.S. initiatives to counter violent extremism, both at home and abroad. Some Members of Congress remain concerned that Europeans fighting with Islamist extremist groups could enter the United States under the U.S. Visa Waiver Program, which allows short-term, visa-free travel for citizens of most European countries (see CRS Report RL32221, Visa Waiver Program). U.S. policymakers underscore the importance of maintaining close U.S.-EU counterterrorism cooperation in light of the Islamist terrorist threat and the foreign fighter phenomenon (see CRS Report RS22030, U.S.-EU Cooperation Against Terrorism).