Thirteen years after 9/11, al-Qaeda has not successfully conducted another attack inside the United States, nor has it conducted any attacks in the West since the bombings on London’s transportation system in 2005. Although individuals inspired by al-Qaeda’s ideology have killed 21 people in the United States since September 2001, a mass-casualty terrorist attack in the United States on the scale of 9/11 is quite unlikely. While each of these deaths is a tragedy, this is nothing like the catastrophic loss of life on 9/11. Al-Qaeda’s leadership has been devastated, and the organization has lost its sanctuary in Afghanistan. Facing destruction, the core al-Qaeda group in Pakistan lacks control over much of the al-Qaeda network and has few means to control the behavior of its affiliates as demonstrated by the Islamic State in Iraq and Syria, which publicly rejected any control by the al-Qaeda core and was formally dismissed from the al-Qaeda network in early 2014.
A number of al-Qaeda-affiliated groups have suffered serious battlefield losses in the past three years. For instance, al-Shabaab once controlled much of Somalia and now it does not; al-Qaeda in the Islamic Maghreb once controlled half of Mali and now it does not; al-Qaeda in the Arabian Peninsula once controlled large chunks of southern Yemen and now it does not; and Jemaah Islamiya once had the capacity to carry out large-scale terrorist attacks in much of Southeast Asia and now it does not. On the other hand, the Islamic State made unprecedented territorial gains in Iraq and Syria, and now it and the al-Qaeda-affiliated Jabhat al-Nusra control more territory in the Arab world than at any time in the history of the modern jihadist movement.
While the core al-Qaeda group that struck the United States on 9/11 has been decimated in recent years, its affiliates and associated groups have diffused throughout the greater Middle East. They now have a presence in 16 countries, more countries than they did half a decade ago. Al-Shabaab’s 2013 attack on the Westgate mall in Nairobi, Kenya, and the 2012 attack by local militants on the U.S. consulate in Benghazi, Libya, demonstrate that even relatively weak terrorist organizations can pull off deadly attacks against local targets. The civil wars in Syria and Iraq (in reality, a regional civil war) and increasing sectarianism across the region have reinvigorated jihadist movements, while the demise of democratic Islamism in Egypt risks creating an Islamist insurgency in a country important to U.S. interests. It is not clear, however, that the diffusion of al-Qaeda-like groups and roiling instability in the Arab world will translate into terrorist attacks against the United States itself, although attacks against American interests overseas will surely remain quite likely.
The spread of al-Qaeda’s ideology combined with new media technologies will continue to foster “homegrown” jihadist extremism. Several incidents—for instance, the 2013 Boston Marathon bombings—demonstrate how jihadist websites can help spawn homegrown terrorism, but on the whole, the threat from homegrown extremists is relatively limited.
Although there are an estimated 100 Americans who have joined or who have attempted to join the fight in Syria as foreign fighters, causing government officials to worry that some might return to the United States to carry out attacks, this has yet to occur. And it may never occur given the similar exodus of more than 40 Americans who fought in Somalia from 2007 onward alongside the al-Qaeda affiliate there, many of whom died on the battlefield and those who did return to the United States did not engage in terrorist plotting. As of early September, while the U.S. government regards the potential threat from ISIS as serious, according to the chairman of the Joint Chiefs of Staff, the U.S. knows of no specific, credible threat from ISIS to the homeland. It’s also worth noting that in none of the successful terrorist attacks in the United States since 9/11, such as the 2013 Boston Marathon bombings or Major Nidal Hasan’s massacre at Fort Hood, Texas, in 2009, did any of the convicted or alleged perpetrators receive training overseas.