The timing certainly looks … intriguing. On Sunday morning, Russian forces raided the compound of an Islamist network once run by Abu Dujan in the Caucasus — a leader whose videos were in Tamerlan Tsarnaev’s YouTube page. The raid killed the brother of the current leader: It could also be a coincidence. Nick Paton Walsh reports for CNN that the Russians have been conducting these raids for months in an effort to tamp down Islamist activities in the Caucasus. The Russians aren’t drawing a connection between the two cases, at least not publicly. However, Abu Dujan’s network operated in Dagestan...