Valery Dzutsev, writing in Eurasia Daily Monitor:
Whether Tamerlan Tsarnaev had some dealings with the Russian security services or with the North Caucasian insurgency—or with both—during his visit in 2012, the fact remains that less than a year after his lengthy trip he appears to have committed a terrorist attack on US soil. This invites a double-pronged response to the external side of the terrorist threat, contingent upon final results of the investigation.
First, the United States may have to start paying greater attention to resolving the conflict in the North Caucasus. The Russian authorities have emphasized that the situation in the region is an internal Russian affair, but in light of the latest events, the situation in the North Caucasus in all likelihood has started to have an adverse effect on other countries and ceased being simply Russia’s domestic matter. Second, the US should decide whether Russia has joined the cohort of states, such as Pakistan, where radicals are trained or inspired to carry out attacks against Western countries. If so, travel and extensive contacts with Russia by certain individuals will likely become more intensely monitored.