The concept of ‘radicalisation’ became particularly significant within research and counter-terrorism practice following the September 11, 2001, attacks. In the aftermath, radicalisation was generally understood as a process through which an individual became ready to support or carry out acts of terrorism.

This study outlines these early post-9/11 understandings of radicalisation as well as a few counter-terrorism practices founded on these ideas. It examines these understandings and practices in light of recent trends, particularly as counter-terrorism authorities increasingly focus on very young individuals whose ideological motivations are often unclear.

The study also highlights that the role of cognitive and ideological radicalisation in terrorism involvement has become increasingly uncertain. Given the centrality of thinking and attitudes to common understandings of radicalisation, and the unclear roles of these domains in terrorism involvement, there is reason to question the future of the concept of ‘radicalisation’ as an explanation of terrorism and as a foundation for counter-terrorism practices.

The article primarily focuses on examples from the UK, which is often viewed as a leader in the field of counter-terrorism.