This is for Allah! shouted the London Bridge killers. But behind that superficial religious rationale, there is much a deeper question: did they do it for each other, for some broader terrorist group such as Isis, or for themselves, as individual “lone wolves” only temporarily allied in mass murder?
Police investigating Saturday’s attack are tracing links between the killers and others, but in doing so they face two very different and recent phenomena: terrorists acting alone, and those inspired, guided and even armed through a virtual network that is hard or impossible to trace.
Salman Abedi, the Manchester bomber, initially appeared to be a lone actor but may well turn out be part of wider network; the London Bridge attackers look like a team but may be only loosely connected to each other and others in the wider community.
The number of so-called lone wolf attacks is increasing, though they are still rarer than attacks carried out by organised groups. A 2013 analysis by the International Institute for Counterterrorism found that attacks by isolated individuals were increasing in number, violence and effectiveness.
A subset of these are “lone wolf packs”, who are only loosely affiliated with each other and may join up only for the attack itself. The term “lone wolf” is debated, however, since it may lend a spurious glamour; some prefer the term “stray dog”.
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Jihadist terrorism has decentralised ever since the September 11 attacks. In 2010 the al-Qaeda magazine Inspire incited attacks by individuals and small independent cells — “lone lions” united only in ideology who had no contact with an identifiable chain of command. The Boston Marathon bombers appear to have been directly inspired in this way.
Isis has embraced the concept of “leaderless resistance”, claiming credit for violence that it had no direct hand in organising, and proclaiming: “The smallest action you do in the heart of their land is dearer to us than the largest action by us.” A parallel development is the virtual plot, which is orchestrated online, providing not just inspiration but recruitment, planning, logistical support and daily encouragement, all at a safe, digital distance. These “remote-controlled” attacks are often co-ordinated from territory under Isis. Those plotting attacks used to meet in person. Counterterrorism officials monitored recruitment hubs using phone interception and surveillance videos.
Isis has been quick to use encrypted communications and social media for online radicalisation and planning in which the attacker and controller never meet. In recent times, what is initially identified as a lone or small cell attack has often turned out to be remote-controlled.
The genuine “lone wolf” and the remote-controlled killer in a network of organised political violence occupy different spaces, psychologically and demographically. Those acting alone tend to be young, less educated and often with mental problems.
A 2015 study in the journal Law and Human Behaviour found that more than 40 per cent of lone terrorists, operating outside a defined command structure and without material assistance have been diagnosed at some point in their life with a mental illness, making them nearly 14 times more likely to be mentally ill than a member of an organised, larger group.
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Those prepared to kill merely on the basis of a general exhortation and a bomb-making recipe on the internet tend to be male, angry, disaffected, and young. A recent article in the Psychiatric Times argued that Isis has marketed violent extremism in the West by providing “existential fast food” to “everyday young people in social transition, on the margins of society, or amidst a crisis of identity”.
Such individuals usually offer some clue online of what they are planning. But not always. As President Obama observed last year: “When you’ve got one person who is deranged or driven by a hateful ideology they can do a lot of damage, and it’s a lot harder to trace those lone-wolf operators.”
Counterterrorism officials identify four broad strands: attackers trained and dispatched by an organisation; those in touch via social media with virtual planners who help to provide targets and technical assistance; operatives in contact with a militant group online but who do not receive specific instructions; and true lone actors who strike without ever communicating with other jihadists.
The last category is the rarest, but also the hardest to track and impede.
Identifying what turns one type of radical into another, or a disaffected youth into a mass killer, is the hardest task of law enforcement. As James Comey, the former FBI director, put it: “We are looking for needles in a haystack, but we’re also called upon to figure out which pieces of hay might someday become needles.”