President Vladimir Putin has long tried to project an image of abundant good health.
Ukrainian officials claimed in May that he is hiding that he is "very ill" with cancer.
Rumors of health problems and secret surgery have followed the Russian president for decades.
Speculation about President Vladimir Putin's health reached fever pitch on Sunday after former MI6 Russia spy Christopher Steele indicated the Russian president could be seriously ill.
Speaking to Sky News, Steele said Putin's health could be a factor in the unfolding invasion of Ukraine.
Since invading Ukraine Putin has had shaky media appearances and has been described - with varying reliability - as suffering from everything from Parkinson's disease to dementia.
Putin has for decades cultivated an image of virile masculinity at peak fitness - but an investigation by independent Russian media outlet Proekt alleged that this was only possible with significant deception.
Most specifics about Putin's health are almost impossible to confirm. His top spokesperson, Dmitry Peskov, has repeatedly denied any issues. Medical professionals have refused to give weight to the rumors, as Deutsche Welle reported, arguing that accurate diagnoses can only be made by in-person examinations.
Here is a timeline of moments when Putin's health has come into question.
October 2012: Kremlin denies looming surgery after hang-gliding accident
In fall 2012, Reuters cited three government sources saying Putin had back trouble and would need surgery soon.
The Kremlin denied this, but after Russian newspaper Vedomosti said that Putin had hurt himself while hang-gliding, Peskov said the trouble was due to "an ordinary sporting injury" in which Putin had strained a muscle, as The Atlantic reported.
November 4 2012: Kremlin suppresses footage of Putin with a limp
By the end of December 2012, Proekt alleged that Putin was wearing a corset and significantly limiting - or even skipping - sit-down engagements due to likely back problems. The outlet cited unnamed Russian officials for the information.
On November 4, Russia's National Unity Day, the Kremlin limited itself to still photos of Putin's appearance at a ceremony in Red Square, according to Proekt. However, footage posted by religious leaders in Moscow showed the president with a slight limp.
2016-2017: At least five doctors with Putin wherever he goes
By matching the check-in dates of medical specialists with Putin's travel schedule, Proekt found that Putin was regularly accompanied by at least five doctors in these years - a number that would later swell to 13.
They included an ENT specialist, an infectious diseases specialist, a staff rescuscitologist, and a neurosurgeon, the outlet reported.
November 2016: Putin disappears for possible back surgery
Between November 25 and December 1, Putin appeared only in pre-recorded meetings, Proekt reported. Meanwhile, 12 specialists suddenly checked in at the Sochi hospital near his residence, including his personal doctors, neurosurgeons, and a rehabilitation specialist, according to Proekt.
May 2017: Putin tumbles during ice hockey crash
Putin, an avid ice hockey player, almost somersaulted when he crashed to the ground during a match in Sochi at the age of 64, CNN reported.
According to Proekt, the player Pavel Bure had crashed into him. After this, an orthopedic traumatologist known to regularly treat the president checked in to a hospital just outside Putin's residence, Proekt reported.
August 2017: Putin disappears with cancer doctors in tow
Between August 8 and 16 that year, the president disappeared from public view, with oncologist-surgeon Evgeny Selivanov, Proekt reported. The presence of an ENT doctor suggested a thyroid issue, the outlet said.
Selivanov joined Putin's medical entourage, flying to his location 35 times in the space of four years, the outlet reported. Only ENT doctors have seen him more often, the outlet said.
February 2018: Putin vanishes with "cold" at height of election campaign
Putin disappeared from view from February 12 to 1 in 2018, just one month before polling day, Proekt reported. Acknowledging his canceled events, Peskov said Putin has a cold, per ABC News.
Fall 2021: An obsession with COVID-19 self-isolation
A COVID-19 outbreak among presidential staff in September last year led Putin to self-isolate for two weeks. Ten days later, he denied any ill health after he was seen coughing during a televised meeting.
Soon after, The New York Times reported that Putin was imposing increasingly stringent isolation procedures on anyone due to see him face-to-face - including isolation for two weeks prior and the requirement to pass through a disinfectant tunnel.
This came weeks after Russia lifted most of its COVID-19 measures nationwide, the paper reported.
By February 2022 - as world leaders implored him not to invade Ukraine - Putin was having his in-person meetings at an extraordinarily long table.
April 2022: Shaky meeting footage fuels speculation
Bizarre footage of Putin meeting with his defense minister on April 21 showed the president gripping the edge of the table, looking uncomfortable and fidgety, as Newsweek reported.
Along with his bloated appearance, the video prompted a welter of tabloid speculation - none of which was confirmed - that he could be suffering from the effects of steroid treatment or Parkinson's disease.
Further unverified rumors were emanated from an anonymous Telegram account claiming to be a former Kremlin insider.
May 2022: Anonymous oligarch says Putin has blood cancer
In early May, New Lines Magazine obtained a recording of an unnamed Russian oligarch saying that Putin "is very ill with blood cancer."
The oligarch, who did not know he was being recorded, went on to criticize Putin's invasion of Ukraine, saying that "we all hope" he dies, and that "the problem is with his head."
May 14: Ukraine says Putin "is very sick" and a coup is under way
Ukrainian intelligence chief Maj. Gen. Kyrylo Budanov told Sky News on May 14 that plans to overthrow Putin were in motion within Russia, and that the 69-year-old was in a "very bad psychological and physical condition and he is very sick."
Putin is sick with cancer, Budanov said. He denied trying to propagate that idea or propaganda to advantage Ukraine.