On Dec. 29, a female suicide bomber blew herself up in the main train station of Volgograd, a city of one million in southern Russia. The explosion killed 16 and wounded scores more. A day later, a similar attack targeted a trolley bus in the same city, killing at least 10. The bombings were a shot across the Kremlin's bow—and a portent of things to come.
The bombings effectively demolish the government's prevailing narrative that, more than two decades after the Soviet Union's collapse, Russia has successfully weathered its own version of the war on terror. In April 2009, Vladimir Putin publicly declared his government's struggle against radical Islam a mission accomplished.
The years since have put the lie to his triumphalism. Islamic militants in the North Caucasus have staged a savage comeback, carrying out atrocities ranging from a brazen suicide raid on the Chechen parliament in Grozny in October 2010 to the assassination of the spiritual leader of Dagestan's moderate Sufi Muslim community in August 2012. Spearheading this violence has been the Caucasus Emirate, Russia's most organized and ruthless terrorist group, which says it seeks "the liberation of the Caucasus" as a prelude to the creation of a regional caliphate in Central Asia.
Russian investigators at a site of the wreckage of a trolleybus after an attack by a suicide bomber in Volgograd, Russia. European Pressphoto Agency
The situation is poised to get much worse because Islamist activity is no longer isolated to the geographic periphery of the Russian Federation. Extreme fundamentalism is also on the rise in Russia's heartland. In Tatarstan and Bashkortostan, both majority-Muslim republics near the Ural Mountains, moderate Islamic clerics have been targets of assassination attempts. Identification with al Qaeda and other radicals, meanwhile, is on the rise. Motorcades bearing the black banners of jihad are now a regular occurrence on the streets of cities in those regions.
Compounding this trouble is the fact that this sprawling nation is on the cusp of major ethnic and religious transformation. Russia's population is constricting rapidly. A recent study by researchers at Russia's Institute of Socio-Scientific Expertise predicted that under a "worst case scenario" the country's population could shrink by nearly a third—to 100 million from roughly 142 million today—by the middle of the century.
Russia's Muslims, however, are faring comparatively well. At some 21 million, they make up roughly 16% of the country's current population. By the end of the decade, one in five Russians will be Muslim—and by midcentury, every other Russian might be.
The Kremlin's policies, meanwhile, have alienated this swelling minority. In all its regions, and especially in the restive ones, Moscow has propped up a succession of corrupt strongmen who have tended to rule by fiat and repression. Simultaneously, as part of Mr. Putin's quest for a strong national identity, his government has aided and abetted the rise of a corrosive xenophobia among its citizens—leaving Russia's Muslims alienated and susceptible to the lure of radical Islam.
Moscow doesn't seem to have a serious answer to the dangerous trends taking place among the Muslim population. Over the past two decades, the Russian government has pursued what amounts to a scorched-earth policy of brutal, low-intensity warfare that has left more than 100,000 of its own citizens dead. In doing so, Russia's leaders have gambled that, no matter how bloody, their approach would remain popular as long as ordinary Russians believed that the threat from radical Islam was both marginal and distant. Yet numerous high-profile terrorist incidents in recent years have increasingly made that look like a losing bet.
This failure is about to become front-page news. The recent bombings in Volgograd have focused world-wide attention on the looming security challenge to the winter Olympics that begin on Feb. 7 in Sochi some 400 miles from Volgograd. Over the summer, Doku Umarov, the emir of the Caucasus Emirate, publicly vowed to attack what he has termed the "satanic" Games. The Volgograd attacks show that he and his followers have the capability to do so.
The Kremlin has staked a great deal of its reputation on the Sochi Olympics, and can ill afford a rerun of the terrorist massacre of the 1972 Munich games. For the West, the Volgograd bombings should raise questions about how Russia is truly faring in its struggle against radical Islam—and whether Moscow's failures could end up affecting Westerners' own well-being.
Mr. Berman is vice president of the American Foreign Policy Council in Washington, D.C., and the author of "Implosion: The End of Russia and What It Means for America" (Regnery, 2013).