Federal prosecutors are trying to piece together the complex web of influences that transformed a young man with no confirmed militant training or links, apparently acting with only the assistance of his younger brother, into a brutal bomber prepared to kill and maim in pursuit of a cause that remained largely unarticulated.
Tamerlan Tsarnaev has become the focal point of a global FBI investigation into whether any organised group or wider conspiracy lay behind last week's Boston Marathon bombings. The 26-year-old, who has been identified through fingerprinting as the man killed in the shootout with police in the Watertown suburb of Boston, is widely assumed to have been the mastermind of the marathon outrage, with his younger brother Dzhokhar Tsarnaev allegedly playing the role of junior partner.
Yet so far the hunt for clues as to the motivation of the Tsarnaev brothers has failed to throw up concrete evidence that they were inspired to militancy by any particular extremist cleric or politician. Nor is there any known link to any nationalist or Islamist group in the Caucasus region that they regarded as their homeland, a link which would suggest they were recruited as foot soldiers and given operational instructions to strike the Boston Marathon.
Federal investigators and counter-terrorism experts are increasingly of the view that the brothers were acting alone. The surmise is that the elder Tsarnaev largely provided his own motivation and training, through the internet.
The idea that the marathon bombings may have been carried out by two men acting as "lone wolves" underlines the daunting task facing counter-terrorism authorities in the US and across the western world. Individual would-be bombers are far more difficult to detect than those operating on behalf of organised groups.
"If there is a link to a terrorist organisation, the probability of them being detected is much higher. The same applies for homegrown terrorism – the more people are involved the more likely they will be detected," said Marc Sageman, a former CIA operations officer who acts as a consultant on political violence to several US government branches.
Tamerlan Tsarnaev has become the focal point of a global FBI investigation into whether any organised group or wider conspiracy lay behind last week's Boston Marathon bombings. The 26-year-old, who has been identified through fingerprinting as the man killed in the shootout with police in the Watertown suburb of Boston, is widely assumed to have been the mastermind of the marathon outrage, with his younger brother Dzhokhar Tsarnaev allegedly playing the role of junior partner.
Yet so far the hunt for clues as to the motivation of the Tsarnaev brothers has failed to throw up concrete evidence that they were inspired to militancy by any particular extremist cleric or politician. Nor is there any known link to any nationalist or Islamist group in the Caucasus region that they regarded as their homeland, a link which would suggest they were recruited as foot soldiers and given operational instructions to strike the Boston Marathon.
Federal investigators and counter-terrorism experts are increasingly of the view that the brothers were acting alone. The surmise is that the elder Tsarnaev largely provided his own motivation and training, through the internet.
The idea that the marathon bombings may have been carried out by two men acting as "lone wolves" underlines the daunting task facing counter-terrorism authorities in the US and across the western world. Individual would-be bombers are far more difficult to detect than those operating on behalf of organised groups.
"If there is a link to a terrorist organisation, the probability of them being detected is much higher. The same applies for homegrown terrorism – the more people are involved the more likely they will be detected," said Marc Sageman, a former CIA operations officer who acts as a consultant on political violence to several US government branches.
