Whose fault is it that the Boston Marathon was bombed? Is Russia to blame for 250 years of trying to incorporate the Muslim North Caucasus nations, like the Chechens and Dagestanis, first into the czars' Christian Orthodox Empire, then into the Soviet Union, and now into President Vladimir Putin's all-controlling Russian state? Or is radical Islam the only explanation we need, both in Russia and the West?

The attack by Tamerlan and Dzhokhar Tsarnaev has invariably elicited comparisons to the Saudi-born terrorists who struck the United States on Sept. 11, 2001, or to the Pakistani immigrant Faisal Shahzad, who attempted to set off a car bomb in Times Square in 2010. Others have suggested that the 26-year-old Tamerlan, an ethnic Chechen, may have witnessed the Russian/Chechen war of 1999, or Russia's brutal efforts to pacify insurgent fighting in the North Caucasus. Overwhelmed by the Russian Army's ruthlessness, it is said, he and his teenage brother chose to spread the violence to U.S. soil.

The problem with this explanation, of course, is that the Tsarnaev brothers were from Kyrgyzstan. They never lived in Chechnya, and only briefly passed through Dagestan in the early 2000s. Their ties with the region are those of the diaspora. Chechen President Ramzan Kadyrov, a former rebel, immediately said that the brothers had nothing to do with his republic.