TWO EXPLOSIONS ROCKED THE MOSCOW METRO system during the morning rush hour Monday. The first attack took place just before 8 a.m. local time at the Lubyanka station, which is just below the headquarters of the Federal Security Service, the modern version of the KGB. The second attack took place 45 minutes later at the Park Kultury station, which is near Gorky Park, one of the city's cultural centers. In addition to the two attacks' symbolic targets, very real damage was inflicted with approximately 35 people killed and more than 100 injured. All signs of the attack suggest that the perpetrators were Muslim and came from one of the Northern Caucasus republics of Russia, most likely Chechnya. Muslim militant groups have a long history of pulling off significant attacks in Moscow, like the Moscow apartment bombing in 1999, the Moscow theater siege in 2002 and the twin airliner bombings in 2004. Such deadly attacks in Moscow — almost 1,000 miles away from Chechnya — are a constant fear for the Kremlin, and a dark reminder of Russia's inherent instability. They also reveal the pressure the Chechens can apply to the Russian government with few resources. As the largest country in the world in terms of land area, Russia is comprised of a vast amount of territory that is home to a broad number of distinct ethnic groups. It may seem counterproductive to attempt to control so many distinct and radically different groups, but Russia's geography and lack of natural barriers necessitates that the country expand its empire as far as possible to create a buffer around the Moscow heartland. This means that to survive as a major power, Russia must control these groups — many of which have different cultures, religions, worldviews and aspirations — to manage the state itself. This problem is one that every ruler of Russia — from Peter the Great to Putin — has had to face. The northern Caucasus is one region that has been particularly difficult for Moscow to control. Due to Russia's size, maintaining control of its territory and people is no easy task. Very often this must be done coercively, which is where the brute military force and the internal security services come in, whether it is czarist, Soviet or modern day Russian. The northern Caucasus is one region that has been particularly difficult for Moscow to control. In addition to the myriad ethnicities and conservative brand of Islam practiced in the region, the mountainous terrain of the Caucasus has bred a fiercely regional and warlike spirit into its inhabitants. The most notorious example of this is Chechnya, with which Russia fought two bloody wars in the 1990s simply to prevent the volatile republic from seceding from the Russian Federation. The Russian state during those wars and under President Boris Yeltsin was fragile and weak and was fighting simply to maintain its territorial integrity. The first war was largely seen as a failure, draining the Russian military's resources and troops. The second war was more successful and led to the emergence of Vladimir Putin, catapulting him into the presidency of Russia. But even though the Kremlin has officially declared the second war a success and inserted tens of thousands of troops into Chechnya, the region has never been fully stabilized. Chechnya is no longer the raging war zone it was in the 1990s, but the Chechens have proven that they can still bring pressure to bear in the way of terrorist attacks. The question now becomes, how much further can Russia go in tackling the Chechen problem? History has shown that it is impossible to completely clamp down on this region, as the endeavor has proven elusive to the Russians, the Soviets, the Mongols, the Romans and so on. Containing the violence and instability to the region has become acceptable for the Kremlin, but once these elements reach out and strike the Russian heartland, it is much more difficult to swallow. Having Chechens fight each other is one thing, but each time the Chechen problem arises in the capital, the Kremlin has reacted swiftly to crush a rising insurgency (whether through war, policing or intimidation tactics). It is possible that there will be a harsh crackdown by the government in response to this most recent attack, but such responses often result in blowback and more radicalization, as Monday's attacks show. And this raises another critical question as to whether the metro bombing was a one-off attack or the return of a more prolonged campaign. Either way, the fundamental problem will still remain: Russia will be inherently unstable as long as it is large enough to include these hostile groups within its borders. Russia is a country with many geopolitical weaknesses, including its exposed core, its need to vastly expand from this core to establish buffer territories, and the hostile and restive populations that these territories can create. Monday's attacks are symptomatic of some these problems, a solution to which no Russian ruler has yet found.