On Monday, the subway system of St. Petersburg, Russia's second city, was the site of a massive bomb blast that killed 14 commuters and wounded more than 50 others. (A second, unexploded device was subsequently found and defused by authorities.) The attack marked the most significant terrorist incident to hit the Russian Federation since December of 2013, when a female suicide bomber blew herself up in the main train station of the southern Russian city of Volgograd ahead of the 2014 Winter Olympics in nearby Sochi.
But it is also much more. Monday's bombing is the latest sign of Russia's worsening terrorism problem, as well as a portent of things to come.
THE COSTS OF SYRIA
Most directly, Monday's attack in St. Petersburg can be viewed as blowback from Russia's ongoing intervention in Syria. Since September 2015, the Kremlin has become a major player in Syria's grinding civil war, establishing a significant - and open-ended - military presence in the country in support of Bashar al-Assad's regime.
Russia's involvement has paid concrete strategic dividends, making it possible for Russia to reinforce its historic naval base at Tartus, establish a new air base in Latakia, and forward deploy an expanded naval force in the eastern Mediterranean, among other gains. But it has also made Moscow the target of Islamist ire, with both the Islamic State (also called ISIS) and Jabhat al-Nusra, al-Qaeda's Syrian affiliate, pledging to retaliate in Russia.
Monday's attack may well have been the start of just such an offensive. Russian authorities have identified the main suspect in the bombing as 22-year-old Akbarzhon Jalilov, a Kyrgyz-born Russian citizen with links to radical Islamists. For its part, ISIS was quick to celebrate the blast (although it stopped short of directly claiming responsibility), suggesting that - at the very least - Jalilov's actions track closely with its own plans for Russia.
RUSSIA'S JIHADI LEGION
Monday's bombing also lays bare a larger problem facing the Kremlin: Russia's Muslims are radicalizing and mobilizing.
Today, Muslims make up the fastest-growing segment of Russian society. They are still a minority at roughly 16 percent of the population, according to the country's 2010 census. But thanks to fewer divorces, less alcoholism, and a greater rate of reproduction, Russia's Muslims are demographically strong. Some projections have suggested that, by the end of this decade, Russia's Muslims could account for a fifth of the country's total population.
But this does not mean that Muslims are well integrated. Russian President Vladimir Putin has championed an ultranationalist identity that has shut out Russia's Muslims from contemporary politics and society, leaving them vulnerable to the lure of alternative ideologies - Islamism chief among them. This can be seen in the growing influence of groups such as ISIS on Russian extremist groups like the Caucasus Emirate, the country's premier jihadi outfit. (In 2015, segments of the group, which had previously been an al Qaeda affiliate, formally pledged allegiance to ISIS and its emir, Abu Bakr al-Baghdadi.) Putin's stance has also led to a growing number of Russian jihadists traveling to join the fighting in Iraq and Syria.
The true size of the Russian contingent in Syria has been the subject of considerable debate. But during a recent public address, Putin indicated that the country's military intelligence service, the GRU, believes that as many as 4,000 Russian nationals, alongside a further 5,000 combatants from other former Soviet Republics, are now participating in the ongoing civil war there.
Putin's revelation was significant, since it suggests that the share of foreign fighters in Syria from the former Soviet Union is far larger than commonly understood in the West. All told, an April 2016 study by the National Bureau of Economic Research estimated that ISIS had succeeded in attracting more than 31,000 recruits to its cause since its rise in 2014. Russian and Central Asian militants may thus account for nearly a third of all foreign fighters now active in the self-proclaimed caliphate. It's no wonder that experts such as Yevgenia Albats estimate that Russian has become the third most frequently spoken language among fighters of the Islamic State.
WORSE TO COME
For a long time, this state of affairs seemed to suit the Kremlin just fine. Far from preventing an outflow of militants to the Middle East, Russian authorities have facilitated their departure as a way of diffusing the country's domestic terrorism problem. At the same time, Putin's government has issued a raft of draconian new regulations - including expanding the definition of what constitutes extremism, requiring official permits for religious activities, and tightening oversight of the Internet - designed to maintain control over potential militants remaining in the country (and everyone else as well).
On the surface, this strategy seems to be working. Kremlin officials have publicly touted their government's counterterrorism successes in an effort to convince the world that Russia is winning its fight against domestic terrorism. In November 2015, for example, Yevgeny Sysoyev, the deputy director of the FSB, Russia's powerful internal security service, lauded the fact that Russia had succeeded in diminishing terrorist activity "by more than ten times" since 2010. But Monday's attack provides a sharp counterpoint - and concrete proof of the country's continued vulnerability to domestic acts of terror.
The problem, moreover, is poised to get far worse. Counterterrorism experts have long been concerned that the Syrian conflict could eventually produce an exodus of former fighters who would return to engage in terrorist activity in their home countries. These fears have become more acute in light of the recent battlefield reversals suffered by ISIS in Iraq and Syria, and signs that the group is now shifting its focus to other theaters.
Given the size of the Russian contingent now present within ISIS, Russia is bound to be a principal target of this trend. Monday's attack in St. Petersburg, in other words, may presage more to come, with all that this portends for the security and liberty of ordinary Russians.