The Caucasus Emirate is an umbrella organization of terrorist groups that has been responsible for a number of attacks in Russia, most recently the bombings of Moscow's metro system. It has been constructed out of the remnants of the anti-Russian groups that existed among the Islamic area around Chechnya before the brutal crackdown that began in 1999. The group appears to be receiving help from Pavel Kosolapov, a rogue Russian soldier and bombmaker who is helping the group manufacture sophisticated devices and training the group to operate in alien environments like, for instance, the Moscow metro.
Most previous Chechen resistance groups took their main aim to be national independence, but the Emirate aims to establish an Islamic state in accordance with Sharia in the Muslim parts of Russia; as such, it adheres to an extreme brand of Islam, and its methods are a brand of urban terrorism and armed propaganda from its position of military weakness. The group has little popular support among the moderate Sufis who make up most of Russia's Muslim population. It hopes to provoke a Russian response that will prompt other Muslims to embrace its aims. Sadly, it may get this wish.
By striking into Moscow, the group is trying to demonstrate to the Russian government that their policy of brutality comes at a cost. Russia treats its Muslim regions like colonial possessions; their inhabitants like fourth-class citizens; and their aspirations as a nuisance. In Moscow, Chechnya seems very far away, and it might be tempting to think this situation can continue. But in Chechnya, Moscow feels very close indeed. The current leaders of the Caucasus Emirate are probably not long for this world, but their chain of successors will likely be endless.