It's a moment many Russian security experts have nervously awaited.
The autocratic leader of former Soviet central Asia's most populous state, Uzbekistan, has reportedly had health scares in the past. But Islam Karimov, who has ruled the nation of about 30 million since Soviet times, was rushed to the hospital on Sunday night in a case that, as described by his daughter in an Instagram message, may signal that political transition is near. In a particularly noteworthy development, it was the first time his health had ever been officially discussed.
As in most central Asian states, Uzbek politics are opaque and there is no obvious successor. Rumors that the dictator's eldest daughter, Gulnara, was angling for her father's job were rife a few years ago, but they died down after she became mired in corruption scandals and was reportedly placed under house arrest.
The mainly Sunni Muslim state, which borders Afghanistan, has never known any leader but Mr. Karimov. Russian experts say that, at least in the short term, the looming succession should be manageable. But the murky nature of Uzbek politics, combined with Islamist groups trying to destabilize the regime, means that the moment is fraught with uncertainty.
"Karimov's inner circle have been preparing for this, they've thought it through, and there surely is someone from their number ready to step in. We just can't say for sure who that is," says Vladimir Sotnikov, director of the independent Russia-East-West Center for Strategic Analysis in Moscow. "We have reasons to believe that a transition, should it become necessary, can be handled smoothly."
Uzbekistan is a poor country, with a closed economy, but it is rich in resources and has enjoyed annual growth rates of more than 7 percent for several years. But poverty and unemployment are serious problems, particularly in the teeming, multi-ethnic Ferghana Valley, which has seen repeated explosions of Islamist-inspired violence. Most serious was a mass insurrection in the Ferghana city of Andijon 11 years ago, put down with exceptional ferocity by Karimov's security forces.
"There is a danger that inner-circle strife could trigger social unrest," says Alexei Makarkin, deputy director of the independent Center of Political Technologies in Moscow. "Islamist influences do exist in Uzbekistan, even if they have been driven underground."
The Islamic Movement of Uzbekistan, a sometime ally of the Taliban and Al Qaeda, would move swiftly to exploit any instability, says Mr. Sotnikov. Though the group's leaders are living in exile in Pakistan, it maintains considerable strength among the ethnic Uzbek population of northern Afghanistan, and could be capable of launching raids inside Uzbekistan as it did in the past.
When the US-led war in Afghanistan began, Karimov offered vital support, including the use of an Uzbek military base at Kharshi Khanabad. But as Uzbek-US relations deteriorated in the wake of the Andijon violence, the Russian and Chinese-led Shanghai Cooperation Organization convinced Karimov to kick the Americans out. Despite some improvements in recent years, relations between the US and Uzbekistan remain strained.
The biggest worry in Moscow is that any outbreak of unrest in Uzbekistan could destabilize the wider central Asian region and become a direct threat to Russia.
"There are also a lot of Uzbek jihadis who've grown disillusioned with the prospects in Uzbekistan and gone off to fight with the Islamic State in Syria and Iraq," Mr. Sotnikov says. "For now the domestic situation appears quiet. But the possibility that Islamist militants could rise again in central Asia is still a very big headache for Moscow. The borders are very porous, and Russia is not far away. Though we may not be expecting a worst-case scenario at this time, there's a lot of evidence that Russian security services are actively preparing for one."