The Washington Post reports that “the evidence so far suggests they were ‘self-radicalized’ through Internet sites and U.S. actions in the Muslim world. Dzhokhar Tsarnaev has specifically cited the U.S. war in Iraq, which ended in December 2011 with the removal of the last American forces, and the war in Afghanistan.”
He also told interrogators that him and his brother, Tamerlan Tsarnaev, acted alone and not at the behest of a foreign militant organization.
The revelation that the attack was motivated by anger at U.S. foreign policy is hardly unique to this terrorist attack. Faisal Shahzad, the naturalized Pakistani-American citizen who tried to blow up a car in Times Square, also cited U.S. foreign policy in the Muslim world as a factor in why he tried to carry out his attack. U.S. drones “kill women, children, they kill everybody,” he said in court."