In Countering Terrorism, Martha Crenshaw and Gary Lafree provide a very detailed account on global acts of terrorism. What makes the subject so challenging? Why is it so hard for governments to formulate an effective counter-terrorism policy? What are the obstacles that experts face and in what ways can terrorism best be defined, classified, studied and understood in order to design the best possible policies to counter terrorism? These are some of the questions answered in this book, which is divided in well-written, clear and understandable chapters.

The book is divided into multiple cohesive and well-structured parts that all discuss different areas of the wider subject of terrorism, from the acknowledgement that terrorist attacks are still relatively rare, to the process of attributing a terrorist attack to a certain group, organisation or party. Crenshaw and Lafree use a wide variety of databases, such as the Global Terrorism Database (GTD), which consists of around 170,000 cases, to support their findings. Arguments rely on data retrieved from these databases, some of which have monitored every terrorist attack since the 1970’s. This enhances the quality of the book.

Crenshaw and Lafree argue that mass casualty attacks – such as the 9/11 attacks, which is still the deadliest attack between 1970 and 2015 – are incredibly rare. The aftermath of such attacks has a profound influence on national and international security policies ­­— policies and regulations adopted after an attack are difficult to reverse. Crenshaw and Lafree also support their argument that terrorist attacks are still relatively rare by stating that in 2012, when there were 15,417 reported terrorism related fatalities, there were 437,000 homicides worldwide.

A significant point discussed in the book are the ‘failed and foiled’ terrorist attacks. Crenshaw and Lafree argue that these types of attacks are more difficult to study and are of less concern to the public. There have, for example, been around a hundred attempted plots to attack American targets post 9/11. Of these attempts, only eight resulted in casualties. But when does an attack fail or foil? Crenshaw and Lafree argue that – according to the Failed and Foiled Plots (FPP) database –  a plot can either be failed or foiled due to malfunction of equipment, change of intention and external intervention. Crenshaw and Lafree define plots as successful when they are physically completed and result in tangible effects.

Crenshaw and Lafree also argue that counter-terrorism policies should be tailor-made for terrorist organisations due to the absence of a single type of terrorist organisation, underlining the differences in structure, objective, ideology and alliances. Without knowing the structure of a certain terrorist organisation, its leadership, cohesiveness and decision-making process, governments struggle to calculate a terrorist organisation’s reaction to certain counter-terrorism policies.  Likewise, creating a working counter-terrorism policy for lone actors without clear affiliation and outside support proves difficult. What makes this difficult is that, although they are not formally part of an organisation, ‘lone wolves’ do identify with the cause of a certain organisation. According to Crenshaw and Lafree, these terrorist threats are so unexpected and unpredictable, that it is impossible to prevent them. For governments to attribute a certain attack to a certain organisation is a difficult process. Often, organisations take credit for acts they did not commit, or those responsible are not known at all. Being unable to punish the responsible perpetrator due to a lack of knowledge or misleading information on the responsible party, makes it, according to Crenshaw and Lafree, increasingly difficult for governments to assert blame on actors, which in return often ensures public unrest. From data, provided in the book, Crenshaw and Lafree conclude that between 1970 and 2015, there were 93,485 unattributed cases and that, overall, only 40.3% of attacks are attributed.

To conclude, Crenshaw and Lafree have shown that defining and measuring the effectiveness of counterterrorism measures is a considerable challenge. Terrorism is a concept that keeps on changing, therefore, counter-terrorism policies should evolve and change as well, based on the specific terrorist organisation and threat posed. The book might be dense in places, but for students, scholars, counter-terrorism experts, government officials and the interested public alike, it is a profound source of useful information that provides clear explanations and data, generated over the course of multiple decades, to give a reliable account on the difficulties of countering terrorism.