It is also probable the Tsarnaevs conducted their attack without any overseas organisation's direction or financial assistance.
How the Tsarnaevs used social media suggests they may have identified with broader causes: that Johar posted his worldview as "Islam" on his social media sites might just be a benign, honest statement of faith; but it could also suggest that he may have identified with a broader ummah (nation or global Islamic community), beyond the brothers' beleaguered co-ethnics.
However, Tamerlan had become more religiously and politically intolerant over the past several years, and began posting extremist videos celebrating violence on his social media sites.
Developments in neo-jihadist doctrines and new and social media provide further insights into how they may have developed a broader worldview and acquired the means by which to perpetrate terrorist attacks.
Neo-jihadist strategist and fighter Abu Musab al-Suri produced the internet-circulated The Global Call to the Islamic Resistance, in 2005. He stresses that the US-led invasion of Afghanistan significantly impeded al-Qaeda's ability to assist similar groups materially and otherwise.
Therefore, it was up to individuals and small groups to finance, prepare for, and execute attacks in their own countries on their own, independent of outside sources of funding, support and instruction.
The book was very influential globally: the leader of the cell arrested in Melbourne in 2005 praised this cyber manual fulsomely and drew on it extensively while he and his colleagues were preparing for a terrorist attack in Australia. It is regarded as the textbook of home-grown terrorism.
That law enforcement in the US and Boston Mayor Tom Menino have indicated that the Tsarnaev brothers probably acted on their own in the attack suggests that they were following at least the spirit, if not the letter of al-Suri's treatise.
Al-Qaeda in the Arabian Peninsula has been circulating the English-language Inspire Magazine to motivate prospective terrorists to conduct these individual or small cell attacks, and to provide them with instructions on how to do so since 2009.
A recent issue of the magazine included instructions on making explosive devices using pressure cookers, and also suggested perpetrators should not claim responsibility for successful attacks.
There is an eerie correspondence between these instructions and what occurred in the Boston Marathon bombings and its aftermath. Forensic experts confirmed the bombs used included parts that had been treated in pressure cookers, and no one claimed responsibility for the operation.
It has not yet been reported whether the Tsarnaevs had seen issues of the magazine.
It remains plausible that the Tsarnaevs may have been attempting to advance a broader Islamist agenda independently of any established entity, and doubtful that they were in league with or advancing a Chechen or North Caucasus cause.
As Tamerlan died following a shootout with police, and Johar is in hospital recovering from serious wounds he received in that fight and attempting to evade arrest, including a throat wound, it remains to be seen if he will tell the world what motivated them.
theconversation.edu.au
Pete Lentini is the foundation director of the Global Terrorism Research Centre at Monash University.
