In Moscow, it was the fiery termination of six years of relative peace. But in the troubled provinces to the east of the Black Sea, the subway bombing was the latest, predictable episode in a year-long tableau of violence that has escalated without much notice from the outside world.
The Russian government, which will be hosting the 2014 Winter Olympics on the edge of this region, has repeatedly reassured citizens and reporters that the wars, slayings and terrorist attacks that spilled from the North Caucasus in the last decade are a thing of the past.
But the female "black widow" bombers who killed at least 38 people Monday in a pair of co-ordinated suicide attacks on the Moscow subway are the latest signs that a second generation of nationalist and Islamic resistance, much wider in scope and less interested in political goals, has spread beyond its base in Chechnya to embrace the entire Muslim-dominated region on Russia's southwestern frontier.
"Many people in Moscow and the West regard this attack as an extraordinary thing, but don't forget that this sort of violence has become a daily thing in the Northern Caucasus," said Andrei Piontkovsky, a Moscow-based analyst.
Just four days ago, Russian soldiers announced that they had killed a senior rebel leader, Anzor Astemirov, in the Northern Caucasus district of Kabardino-Balkaria. He was said to have been the top ally of Chechen leader Doku Umarov, who has become the unchallenged "emir," or warlord-governor, of southern Chechnya and has been spreading his Islamist rule across the neighbouring republics of Ingushetia and Dagestan.
A few weeks before that, Russian soldiers killed 20 insurgents in retaliation for a November bomb attack on the Moscow-St. Petersburg express train carried out by Mr. Umarov's forces.
This month alone has seen two assassination attempts on Russian officials in Ingushetia and at least six bombings in Dagestan, all of them considered linked to Mr. Umarov. In exchange, Russian forces claim to have killed 35 nationalist and Islamist leaders in Ingushetia and Dagestan this year, under increasingly warlike conditions.
Mr. Umarov seems to be the force behind yesterday's bombings. In February, he issued a statement vowing to take his regional battle to the cities of Russia. He had earlier stated that there were "no civilians" in Moscow, that all Russians are guilty by association with the crimes of their leaders.
"Blood will no longer be limited to our region's cities and towns," he wrote on the rebel-supporting website kavkazcenter.com. "The war is coming to their cities." The site yesterday posted articles blaming the deaths in Moscow on the actions of Russian forces in the Caucasus.
Indeed, Russian leaders seem to accept this explanation. Viktor Ilyukhin, deputy chair of the State Duma security committee, acknowledged yesterday that the attacks are likely the result of Islamist and nationalist movements that have been spreading quietly across the Northern Caucasus under the watch of Moscow-controlled leaders there.
"The terrorists are aiming at destabilization; their goal is the frighten the population," Mr. Ilyukhin said in an interview with Russian media. "They also want to take revenge for the actions of the security forces against them, for the arrests and liquidations of their leaders."
Both the location and the date of yesterday's attacks were symbolically loaded. This week marks 10 years since Vladimir Putin was elected to the presidency on a pledge to stamp out the Chechen rebellions that had arrived in Moscow in the form of a string of deadly apartment-building bombings. The stations where the bombs went off are used by the officers and staff of the security agencies that carried out Mr. Putin's subsequent crackdown on Chechen independence.
That women carried out the attacks was not unusual either. Female suicide bombings became common in the early 2000s, and bomb-carrying Chechen women were used in a deadly hostage-taking at a Moscow theatre in 2002.
Known as "black widows" in the Russian media and among their own people as shakhidy, or martyrs, their ranks are drawn from women who have been gang-raped by Russian soldiers or who have lost sons and husbands in the conflict, which has seen atrocities committed by both sides for years. The black widows have carried out numerous attacks, including previous bombings on the Moscow subway.
After the Beslan school massacre in 2004, an atrocity in which Chechen separatists killed more than 300 people - half of them children - opinion turned against the Chechen cause. That, combined with a Russian crackdown, led to the rebuilding of a relatively peaceful Chechnya under the leadership of pro-Moscow strongman Ramzan Kadyrov.
Mr. Kadyrov's rule was considered a successful example of the use of what by Russian standards amounted to "soft power." Although he employed violent repression, Mr. Kadyrov embraced the local brand of Islam, which is peaceful and culturally European, allowing its mosques to flourish while driving out the Saudi-influenced militants who had proliferated during the years of war.
Moscow branded this a success. But over the last six years the militants have moved out from central Chechnya to spread their influence across the neighbouring republics of the North Caucasus, a much larger region that is more difficult to police. There, they have established several centres of Islamic rule beyond Moscow's control.
Russian officials who oversee the region seemed to have been taken by surprise by Monday's events. "There has been a quiet period after administrative and organizational measures had been taken. … It seems that the terrorists had accumulated strength and money for attacks," said Mikhail Grishankov, the first chairman of the Duma security committee.
What is alarming about these second-generation movements, Russian observers say, is that they lack the separatist ambitions of the Chechens. Instead, they have embraced Saudi-style Wahhabi Islam and are intent on spreading religious rule.
Unlike their predecessors, these rebels' terrorist attacks are not accompanied by political or military demands.
"In Chechnya, all separatist ambitions have been achieved already, so it's not a force," said Mr. Piontkovsky. "The real driving forces of violence, of rebellion in the republics, are not separatism but are Islamic fundamentalism. They want terror for its own sake, to convert people and get revenge."
The risk is that Russia will return to the strategy it initially used against the Chechens: the imposition of overwhelming force, employing an expensive military strategy and costing tens of thousands of lives over many years. A war on this scale across the wider North Caucasus could be devastating.
Without addressing such longer-term questions, President Dmitry Medvedev yesterday vowed to crack down hard. "The policy against terror in our country will continue," he said in a statement. "We will continue operations against terrorists until the end, with no hesitation."