There are reports that the brothers are originally from Chechnya or near Chechnya. CFR has a useful 2010 primer on terrorism inside the country:
From 1994 to 1996, Russia fought Chechen guerillas in a conflict that became known as the First Chechen War. Tens of thousands of civilians died, but Russia failed to win control of Chechnya’s mountainous terrain, giving Chechnya de facto independence. In May 1996, Yeltsin signed a ceasefire with the separatists, and they agreed on a peace treaty the following year.
But violence flared again three years later. In August 1999, Chechen militants invaded the neighboring Russian republic of Dagestan to support a local separatist movement. The following month, five bombs exploded in Russia over a ten-day period, killing almost three hundred civilians. Moscow blamed Chechen rebels for the explosions, which comprised the largest coordinated terrorist attack in Russian history.
The Dagestan invasion and the Russian bombings prompted Russian forces to launch the Second Chechen War, also known as the War in the North Caucasus. In February 2000, Russia recaptured the Chechen capital of Grozny, destroying a good part of the city center in the process, reasserting direct control over Chechnya. Tens of thousands of Chechens and Russians were killed or wounded in the two wars, and hundreds of thousands of civilians were displaced. Since the end of the second war, Chechen separatist activity has diminished, and the July 2006 death of separatist leaderShamil Basayev–in an explosion many see as the work of Russia’s internal security services–seems to have stifled the movement.
But USA Today points out that, in recent years, Chechen terrorists still “committed sporadic large-scale attacks in Russia”:
In March 2010, Chechen terrorists claimed responsible for bombings on the Moscow subway system that killed more than 40 people. In June 2010, the State Department added Chechen rebel Doku Umarov, who claimed responsibility for the March subway attack, to its terrorist list and froze his assets. The reduced turmoil inside Chechnya has been the result of massive efforts by the Russian security forces.
Hayes Brown adds:
Unfortunately, this does not tell us very much at the moment. An ethnicity does not indicate any sort of defined motive or ties to any possible group or groups and law enforcement has yet to provide any confirmation of the current reporting. Chechen groups also have traditionally focused their ire on Russia rather than targeting the United States. Finally, given their lengthy residence it is difficult to discern what — if any — ties or sympathies the two brothers have to Chechen terrorist groups. The older of the brothers — Tamerlan Tsarnaev — has been in the United States since as early as 1992 as a refugee and in 2002 hoped to box for the United States at the Salt Lake City Olympics.
The Dish 