Who was behind the jihadist attacks on Europe and North America?
More than 400 people have died in jihadist attacks in the West during the past three years. What can we learn, asks Dr Lorenzo Vidino.
Although the vast majority of Islamist attacks are elsewhere in the world, an unprecedented number in Europe and North America - more than 50 in total - have put the authorities under great pressure to prevent further deaths.
What do we know of the individuals who carried out the attacks - their life in the West, whether they were known to the authorities and with whom they were working?
The first look at the data behind the attacks - everything from the age of the perpetrators, to immigration status - offers counter-terrorism officials, and the public, an insight that could help them identify the best responses.
Where the attacks were
We identified 52 attacks between December 2014 and early June 2017 that we considered to be acts of jihadist terrorism.
This period follows the declaration of a "caliphate" by the so-called Islamic State in parts of Syria and Iraq in June 2014.
A relatively limited number of countries were affected.
Six were in Europe: France - the worst affected country, Germany, the United Kingdom, Belgium, Denmark and Sweden.
There were also attacks in the United States and Canada.
Regardless of country, most attacks were in large towns and cities - including London, Paris, Nice, Berlin, Brussels and Orlando.
Many others targeted crowded spaces such as busy pedestrian areas, entertainment venues or transport hubs.
How the attacks were identified
We looked at attacks motivated by jihadist ideology, that involved deliberate acts of violence against other people and were intended to intimidate or convey a message to a larger group. Other organisations use different definitions.
- Researchers used open-source material and interviews with officials
- It is possible that some attacks did not come to our attention, or that full details are not available
- The research covers the US, Canada and the 28 member states of the EU, plus Norway and Switzerland
- Attacks motivated by other ideologies - such as the murder of Jo Cox - are not included in this study
The dead and injured
In total, the 52 attacks caused 403 deaths and left more than 1,600 people injured.
The perpetrators are not included in these figures.
France also saw the Nice lorry attack, which left 86 people dead.
There were many other attacks that left many people dead and others injured.
- In Orlando, 49 people were killed in an attack on a gay nightclub
- Bombings at Brussels airport and at a metro station left 32 people dead
- 14 people were killed at a Christmas party in San Bernardino, California
- 12 people died when a lorry was driven into a crowded Christmas market in Berlin
- 12 people died when the Paris offices of Charlie Hebdo were attacked in January 2015
- Five people were killed in the Westminster attack in April
- The Manchester Arena bombing in May led to 22 deaths
- The London Bridge attack in June left eight people dead
In total, these 10 attacks were responsible for 370 deaths.
However, most of the attacks did not cause casualties, with the exclusion of the perpetrators.
Who the attackers were
Although the number of young people being radicalised has caused concern, the average age of the attackers - 27 - is not unusually young.
Of the five who were under the age of 18 at the time, four were in Germany.
The vast majority of the attackers were in their 20s, with about one in four attackers above the age of 30 and three aged 40 or older.
The oldest attacker, Khalid Masood, was 52 when he drove into pedestrians on Westminster Bridge and stabbed to death a police officer at the Houses of Parliament.
It is noteworthy that the older perpetrators were twice as likely to have been imprisoned and to have a history of substance abuse.
Despite women becoming increasingly active in jihadist networks, only two out of 65 individual perpetrators were female.
Fewer than one in five perpetrators was a convert to Islam, with a significantly higher percentage in North America than in Europe.
Background of the attackers
82% were known to the authorities before attack
57% had a criminal background
34% had served time in prison
73% were citizens of the country of attack
However, the converts were significantly more likely to have a criminal background and to have served time in prison.
Overall, most of the attackers had a prior criminal background.
- How can police stop terror suspects travelling?
- Is terror more of a threat to Europe than before?
- Terror deaths in Western Europe at highest level since 2004
- Can you monitor every suspect?
The relationship between terrorism and migration is a complex one and has been at the centre of extremely polarising debates, particularly during the European migrant crisis.
However, the number of attackers who were illegally in a country or who arrived as refugees is small.
Three-quarters were citizens of the country they attacked, with others either legal residents, or legal visitors from neighbouring countries.
However, individuals who were in the West illegally also carried out deadly attacks.
At least two of those involved in the November 2015 Paris attacks are thought to have posed as refugees to enter Europe through Greece.
Three other individuals were refugees or asylum seekers at the time of attack, while four were in the country illegally or awaiting deportation.
The latter group includes Uzbek national Rakhmat Akilov, who killed four people with a hijacked lorry in Stockholm in April 2017, and Tunisian citizen Anis Amri, who also used a lorry to commit his attack at the Berlin Christmas market.
There is also one case of "terrorist tourism", involving Egyptian citizen Abdullah Hamamy, who lived in the United Arab Emirates and attacked soldiers at the Louvre in February 2017.
Links to IS
Two of the four most lethal attacks - those in Paris in November 2015 and in Brussels in 2016 - are believed to be well orchestrated multiple attacks directed by IS.
They were also executed in part by former foreign fighters.
However, the two other most deadly attacks - those in Orlando in June 2016 and in Nice in July 2016 - were carried out independently by individuals without operational connection to a jihadist group.
These episodes demonstrate that terrorist sympathisers who never travelled to conflict areas and who act independently can be as dangerous as a team of highly trained militants.
Overall, links between attackers and jihadist groups operating overseas are not always easy to determine.
Of the attacks that have hit the West since June 2014, fewer than one in 10 was carried out under direct orders from the leadership of IS.
Nevertheless, the influence of IS can be clearly seen.
During or before the attack, six out of 10 perpetrators pledged allegiance to a jihadist group, almost always IS - which frequently claims responsibility.
Learning the lessons
Unsurprisingly, given the frequency of attacks and the number of deaths and injuries, jihadist terrorism has come to the fore of political debates in the West and receives widespread news coverage.
The threat is not expected to wane in the near future, with policymakers, counter-terrorism officials and the public all being asked to take action.
There are huge implications for domestic and foreign policy throughout Western countries.
It is hoped that knowing more about the attacks and the people who carried them out will help us all have a more informed debate about what action is needed.
About this piece
This analysis piece was commissioned by the BBC from an expert working for an outside organisation.
- Dr Lorenzo Vidino is the director of the Program on Extremism at the George Washington University and of the Program on Radicalisation and International Terrorism at the Italian Institute for International Political Studies (ISPI) in Milan
- This research is part of a report by ISPI, George Washington's Program on Extremism and the International Centre for Counter-terrorism in The Hague, conducted by Dr Vidino, along with Dr Francesco Marone and Eva Entenmann
- Full report: Fear Thy Neighbor. Radicalization and Jihadist Attacks in the West