WASHINGTON — Aware that intensified American counterterrorism efforts have made an ambitious Sept. 11-style plot a long shot, al-Qaida propagandists for several years have called on their devotees in the United States to carry out smaller-scale solo attacks and provided the online education to teach them how.
“I strongly recommend all of the brothers and sisters coming from the West to consider attacking America in its own backyard,” wrote Samir Khan, an American who joined al-Qaida’s Yemen branch and emerged as a fervent advocate of homegrown, do-it-yourself terrorism before he was killed in an American drone strike in September 2011.
“The effect is much greater, it always embarrasses the enemy, and these types of individual decision-making attacks are nearly impossible for them to contain,” Khan wrote in a Web publication.
The Boston Marathon bombing — which the authorities believe was carried out according to instructions that Khan posted online — offers an unsettling example of just how devastating such an attack can be, even when the death toll is low. It shows how plotters can construct powerful bombs without attracting official attention. It offers a case study in the complex mix of personality and ideology at work in extremist violence. And it raises a pressing question: Is there any way to detect such plotters before they can act?
The bombing killed three people, compared with 3,000 in the 2001 attacks. But it achieved the spectacular media impact that terrorists covet, marring an American institution with television footage of gruesome injuries and panicked crowds. Officials are worried about its copycat appeal.
The Boston case remains under investigation, and some facts set it apart from other domestic plots. FBI agents are still studying whether Tamerlan Tsarnaev, 26, who investigators believe carried out the attack with his younger brother, Dzhokhar, 19, received any training during a six-month visit last year to turbulent Dagestan in southern Russia. Intelligence agencies are reviewing whether two Russian warnings about the older brother in 2011 were handled properly.
At a news conference on Tuesday, President Barack Obama suggested that the bombers had acted on their own, saying that “one of the dangers that we now face are self-radicalized individuals who are already here in the United States.” Obama said such plots “are in some ways more difficult to prevent.”
So far, the Tsarnaev brothers appear to have been radicalized and instructed in explosives not at a training camp but at home on the Internet. Their bombs were concocted from inexpensive everyday items whose purchase set off no alarms: pressure cookers, nails and ball bearings, gunpowder from fireworks and remote controls for toys.
In other words, as Dzhokhar told investigators, they followed the script from Inspire magazine, which Khan published in Yemen along with his mentor, the cleric Anwar al-Awlaki, who was killed in the same drone strike on Sept. 30, 2011. Al-Awlaki’s incendiary sermons and Khan’s training articles survived them on the Web, where the brothers found them.
Just a month before the Boston attack, the al-Qaida branch in Yemen posted on the Web the “Lone Mujahid Pocketbook,” a compilation of all the do-it-yourself articles with jaunty English text, high-quality graphics and teen-friendly shorthand.
“R U dreamin’ of wagin’ jihadi attacks against kuffar?” the 64-page manual asks, using a pejorative term for unbeliever.
Some of the manual’s ideas seem harebrained — spilling oil on the road to cause car wrecks or welding blades to a pickup truck and driving into a crowd. But specialists say its bomb-making instructions are quite accurate. The Boston attack seems to have followed Inspire’s tips: gunpowder emptied from fireworks, shrapnel glued inside the pressure cooker, a commercial remote control as detonator.