Investigators will be tracking suspect’s recent experiences in the US but will also be digging into his formative years abroad

Early reports say Akayed Ullah, the suspect in Monday’s attack in New York, is originally from Bangladesh and has been in the United States for seven years. Officials believe Ullah was inspired by Islamic State, which is entirely plausible given other recent plots, though this should become clearer in coming days.

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Investigators will now be piecing together the 27-year-old’s biography. They will be looking for clues about his potential radicalisation. Much of their focus will be on recent days and weeks, but they will also be digging deep back into his youth in his native land.

Bangladesh is often overlooked by analysts but the unstable and poor Muslim-majority country of 160 million people has experienced an acute intensification of jihadist activity in recent years.

The most spectacular attack came in July last year when 22 people – including 18 foreigners - were killed at a restaurant in an upscale neighbourhood of the capital, Dhaka. Isis claimed responsibility.

Facebook Twitter Pinterest Akayed Ullah is thought to have been in the US for seven years. Photograph: AP

Smaller attacks have targeted secular bloggers, writers, religious minorities and foreign aid workers. Al-Qaida is active in the country, as are a range of autonomous local groups.

As usual, the violence has deep roots: unresolved social, political and cultural tensions between religious conservatives and secular leftists dating back to the 1971 civil war; huge numbers of young men who have limited skills, education and opportunities living in dysfunctional cities and towns; the expansion of conservative Islamic institutions funded by Gulf donors.

Then there are the recent atrocities directed at neighbouring Myanmar’s Rohingya minority – and the arrival of hundreds of thousands of refugees. These have reinforced a narrative of global attacks on Islam that is a key theme of the propaganda of violent and non-violent Islamists alike.

This has been exacerbated by political failings. Policymakers in Bangladesh have sought advantage from extremism, tended to blame others for their domestic problems and taken only tardy action against militant networks. Senior officials blamed the victims of some attacks for “insulting” Islam, and for a long time denied the presence of either al-Qaida or Islamic State in the country.

Yet the numbers of Bangladeshi volunteers fighting for either organisation overseas have been small compared with other large nations. Several British citizens recruited by Isis have been of Bangladeshi origin, but this only underlines the difficulties of seeking to explain the immediate choices of such individuals by reference to their place of birth.

Connections with a distant native land can be important. Several attackers in the US in recent years with origins in south Asia – notably Pakistan – have been trained, funded or otherwise assisted by militant groups based where they or their parents grew up. The Manchester bomber’s close links to Libya were key to his radicalisation and execution of his attack in May this year.

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But the radicalisation of the two men who attacked the Boston Marathon in 2013 had little to do with the central Asian states where they grew up. Nor did that of Ahmad Khan Rahimi, the Afghan-American recently convicted of carrying out a two-day bombing spree in New York and New Jersey in September 2016.

Most research shows the factors that can produce a violent domestic extremist can come together rapidly: a network of like-minded peers, exposure to a particular leader, a contact on the internet, a sudden personal shock or disappointment, a thwarted ambition to travel to a far-flung foreign battlefield.

The stories of most recent attackers in the west suggests the primary drivers of their violence are more recent experiences in their new homes, not a legacy of their early lives thousands of miles away.