In recent years, radical changes have transformed the international terrorism landscape, with violent extremists helping to destabilize several Middle Eastern and North African countries and attacks by homegrown terrorists plaguing the West. In the Middle East, the Islamic State of Iraq and the Levant (ISIL) has taken over a third of Iraq and Syria, subjecting residents to a harsh form of Islamic law and persecuting or killing those they consider enemies. Currently, however, U.S. officials believe that Yemen-based al Qaeda in the Arabian Peninsula (AQAP) presents the greatest threat of a catastrophic attack on the United States. Potential “lone wolf” attackers, among those returning home from Syria and others radicalized by online propaganda, also pose a threat to both the United States and other Western countries

Kurdish demonstrators in front of the White House on Aug. 9, 2014, protest terrorism by the so-called Islamic State (ISIS), which conquered large swaths of territory in Iraq and Syria last summer. ISIS has recruited thousands of young Muslims from Western and Muslim countries. (AFP/Getty Images/Mandel Ngan)

The past 18 months have been tough for Western countries struggling to combat terrorism. While violent extremist groups threaten the stability of several countries in the Middle East and Africa, the number of small attacks in the West — by individual extremists, several of whom had become radicalized by online jihadist propaganda — has spiked. And although few people died in these attacks, they raise concerns.

The United States faces “a much greater recurring threat from lone offenders” than from so-called transnational terror groups, said Nicholas J. Rasmussen, director of the National Counterterrorism Center (NCTC), which aggregates U.S. intelligence for law enforcement and intelligence agencies.1 In a House committee hearing in February, he estimated that the threat from homegrown violent extremists in the United States will remain at “fewer than 10 uncoordinated and unsophisticated plots annually.”2