In warzones, ordinary commercially-available drones are used for extraordinary reconnaissance and information gathering. They can also be used for bombings a drone carrying an explosive charge is potentially a powerful weapon. At the same time asymmetric warfare has become the norm with large states increasingly fighting marginal terrorist groups in the Middle East and elsewhere. In Drones and Terrorism, Nicholas Grossman shows how we are entering the age of the drone terrorist – groups such as Hezbollah are already using them in the Middle East. Grossman will analyse the ways in which the United States, Israel and other advanced militaries use aerial drones and ground-based robots to fight non-state actors (e.g. ISIS, al Qaeda, the Iraqi and Afghan insurgencies, Hezbollah, Hamas, etc.) and how these groups, as well as individual terrorists, are utilising less advanced commercially-available drones to fight powerful state opponents. Robotics has huge implications for the future of security, terrorism and international relations and this will be essential reading on the subject of terrorism and drone warfare.

In this extract, Nicholas Grossman looks at the rise of ‘signature strikes’, a controversial technique that is dividing opinions on its efficiency.

In June 2015, the American drone campaign claimed its highest value target, killing Nasir al Wuhayshi, the leader of AQAP, in Yemen. Al Wuhayshi united jihadists fighting in Yemen and Saudi Arabia, bringing them together under the Al Qaeda banner and transforming the group into a local and international force.

In addition to publishing Inspire, AQAP is responsible for more attempted attacks against Western targets since 2008 than Al Qaeda Central. Along with equipping the underwear bomber, AQAP placed three bombs made with PETN—a difficult-to-detect plastic explosive—hidden inside printer cartridges on cargo planes bound for Western cities in 2010.

One caused a fire on a UPS flight shortly after it took off from Dubai towards Cologne that killed two crew members on September 3, 2010. Acting on a tip from Saudi intelligence, authorities found the other two on October 29, on planes bound for Chicago. The bombs appeared designed to detonate in the air as the planes approached their destinations, destroying the aircraft and raining debris down on whatever was below.

The United States killed Al Wuhayshi with a controversial technique known as a “signature strike.” Unlike attacks in which American intelligence identifies and deliberately targets a specific individual, signature strikes target people whose location and actions “match a pre-identified ‘signature’ of behavior that the U.S. links to militant activity.” Critics argue that even when signature strikes kill members of a terrorist organization they are morally questionable, because many “individuals killed are not on a kill list, and the government does not know their names.”

Additionally, some assert that signature strikes cause significant backlash, angering people in targeted countries, primarily Pakistan, which makes them less likely to cooperate with the United States and aids terrorist recruitment. However, while public opinion research shows considerable anger in Pakistan over the American drone campaign, there is no evidence this anger derives from a specific objection to signature strikes, rather than a more straightforward objection to the United States killing people in Pakistan.

An unmanned US aircraft launches a missile over Northern Pakistan, 2013

Signature strikes are an attempt to overcome the United States’ informational disadvantage. Al Qaeda know the identity and location of group members, but the United States does not. Drones can help compensate with aerial intelligence, but while they can track someone identified by more traditional intelligence techniques, it is hard to identify a specific person from high in the air. Given this difficulty, the United States has supplemented efforts to follow and target known individuals by monitoring areas with militant activity and attacking based on observed behavior rather than specific identities. This leads to some successes, such as the attack that killed al Wuhayshi, but also some notable failures. For example, an August 2012 strike in Yemen killed an imam who had been working to dismantle Al Qaeda in the Arabian Peninsula.

Killing innocents is morally problematic, and in this case a significant strategic setback. Muslim religious leaders speaking out against jihadist organizations can counter the groups’ ideological appeal. Additionally, since signature strikes target behavior rather than specific individuals, they often kill low-level militants who are easily replaceable, which is a small benefit relative to the risk of killing civilians or potential allies like the Yemeni imam. Nevertheless, signature strikes’ ability to kill high value targets such as al Wuhayshi and Adam Gadahn create enough benefit that the United States will probably continue employing the technique, at least to some degree.

Nicholas Grossman is Assistant Teaching Professor of International Relations at the University of Illinois and Editor-at-Large of Arc Digital. He is an expert on robotics, drones, terrorism, insurgency, and US foreign policy, and his writing has appeared in Arc, National Review, CNBC Opinion and elsewhere.

Drones and Terrorism: Asymmetric Warfare and the Threat to Global Security is available to order now from the I.B.Tauris website.