Screen Shot 2013-04-21 at 8.37.22 AMIn his State of the Union address to the American people earlier this year, Barack Obama declared that he was “confident” of achieving “our objective of defeating the core of al-Qaeda”.

Although he acknowledged the need to pursue the “remnants” of the terrorist group and its affiliates, the overall message was clear – al-Qaeda was badly degraded, the tides of war were receding and the US was winning this fight that was no longer even officially a war.

The Boston bombings would appear to present a fundamental challenge to that assessment and once again bring the nagging uncertainty of terrorism back on to the American main street.

It is too soon to be absolutely sure the attacks were motivated by jihadist ideology, but the Islamic videos on the website of the older of the two Tsarnaev brothers point very firmly in that direction.

They bring home the complexity of the global Islamist threat and the fact that it cannot be confined to wars in distant lands, or fought at arm’s length using drones, as the Obama administration has quietly yet insistently led America to believe.

Read more: telegraph.co.uk