Unlike other people in Putin's inner circle, Shoigu was not educated in St. Petersburg or Moscow.
In 1977, Shoigu graduated from the Krasnoyarsk Polytechnic Institute in Siberia with a degree in civil engineering. He went on to work on a variety of major construction projects in the region.
"Shoigu is the only figure within Russian President Vladimir Putin's inner circle who isn't either an old KGB buddy or an old friend from St. Petersburg," Mark Galeotti, who heads the Russia-focused consultancy Mayak Intelligence, told Insider.
Putin was born and studied in St. Petersburg and spent much of his early career there.
Despite being Russia's Defense Minister, Shoigu never served in the military.
He wears awards on his uniform that look like combat medals, despite his lack of battlefield experience.
Shoigu's official profile lists a string of presidential and state awards for his time in government, while his Russian-language Wikipedia page lists more than 70 separate honors.
They include medals from his own defense ministry for implementing policies there, and also mass awards marking events like the 300th anniversary of the founding of St. Petersburg.
After working in various roles for construction companies in Siberia, Shoigu moved to Moscow in 1990 to lead the state's committee for construction and architecture.
In 1991, while he was there, the Soviet Union collapsed, plunging Russia into a period of instability and unrest.
Out of the chaos, Russia gained its first president — Boris Yeltsin, a personal friend of Shoigu. He was soon promoted to lead the newly-established Russian Rescue Corps.
In the Russian Rescue Corps, Shoigu was responsible for the rescue and disaster response system, The Moscow Times reported.
His career there soon took off.
In his role, Shoigu would be the first to appear at any major or minor disaster sites, presenting himself as a hero.
"He had a big PR team, let's be perfectly honest," Galeotti told Insider.
He stayed on the job for 21 years, even after Russian President Vladimir Putin took over from Yeltsin.
As the president of the Russian Geographical Society, Shoigu would also indulge Putin's interest in the outdoors.
"Putin and Shoigu are both throwbacks to Soviet times. They regard themselves as 'muzhiks' (real Russian men) who love sports and hunting," British magazine The Spectator observed in 2015.
This interest may have taken a surreal, even macabre turn.
Russian investigative news outlet Proekt reported in April that Putin has taken up bathing in blood extract from severed deer antlers as a form of alternative medicine. The bath is believed to improve the cardiovascular system and rejuvenate the skin
The unusual remedy was a suggestion made by Shoigu, the report said.
At one point in his career, Shoigu was touted to be the next prime minister.
In the early days of his role as minister of defense, Shoigu was considered the second most popular public figure in the country and was even touted as Putin's potential successor.
One day after Russia's invasion, Shoigu was personally sanctioned by the West.
Other members of Putin's inner circle who were sanctioned alongside Shoigu included Minister of Foreign Affairs Sergei Lavrov and Chief of the General Staff of the Armed Forces Valery Gerasimov.
Several days before Putin's full-scale invasion in February, Shoigu met with British Defence Secretary Ben Wallace and denied Russia was planning to attack Ukraine.
This was despite Western intelligence services publishing extensive evidence of Russian troops amassing near Ukraine's borders, and claims from figures including President Joe Biden that an invasion was inevitable.
But when Russia did invade on February 24, it did not pan out the way the Kremlin had planned.
Russia seemed to expect it could take Ukraine's capital Kyiv in a matter of days, but failed to do so.
For months, their forces have struggled in the face of a staunch Ukrainian resistance that continues to receive more heavy weaponry from Western allies.
The failures in Ukraine have led to claims of a rift between Shoigu and Putin.
One month after Russia's invasion, there was "persistent tension" between the two friends after it emerged that Shoigu and his subordinates were sugar-coating reports of the war for Putin, The New York Times reported at the time.
In March, Shoigu wasn't seen in public for 12 days, prompting concerns over his whereabouts, The Guardian reported.
In August, Putin started to bypass Shoigu, further embedding himself into the war's strategic planning efforts, The Telegraph reported.
Other prominent figures in the Kremlin have openly attacked Shoigu, including Russian oligarch Yevgeniy Prigozhin.
Yevgeniy Prigozhin, who founded the Wagner Group paramilitary, confronted Putin about the mismanagement of the war in Ukraine last month, two US officials familiar with the matter told The Washington Post.
Prigozhin later denied that he had spoken to Russia's president and said he has no right to criticize Russia's army.
Kirill Stremousov, a pro-Russia Ukrainian politician who was installed as Putin's puppet leader in the occupied Ukrainian region of Kherson, recently suggested Shoigu should consider killing himself over Russia's recent military losses.
Stremousov was killed in a car crash in Kherson on November 9, local officials said, according to the BBC.
He died hours before Shoigu ordered the withdrawal of his troops from the city.
"Shoigu is willing to basically be Putin's bulletproof vest," said Galeotti, the Russia analyst.
"He is soaking up all the criticism that, otherwise, people might start leveling towards Putin as commander in chief," Galeotti said.
Shoigu has remained quiet despite the growing criticism...
"He's been much less evident now," Galeotti told Insider.
"He knows that, when he goes into public, he either has to reassure people that everything's going fine, which is an increasingly untenable position to hold, or he'd have to acknowledge things are going badly, which would potentially sound like criticism of the commander in chief," he added.
... and Putin has shown no signs that he may fire him.
Galeotti told Insider that it is difficult for Putin to fire Shoigu because it is "a card he can only play once."
"If Putin absolutely felt that the situation demanded it, I imagine he would be willing to sacrifice Shoigu," he said.
"However, given that it's obviously not going to have any substantive impact on the progress of the war ... it will be harder to avoid the suspicion that it's not because of Shoigu, but because of Putin."
On November 9, Shoigu ordered his troops to retreat from Kherson, the only major city in Ukraine that Russian forces were able to capture during the invasion.
The retreat was a huge blow to Shoigu, who only a month before had told Putin that his goal to send 300,000 of Russia's reservists to fight in Ukraine had been completed, Reuters reported.
After all the retreats, Shoigu stepped up his rhetoric in November, saying that Russia should use new advanced weapons systems in Ukraine.
Shoigu did not specify which advanced weapons should be used, though he said he is looking at new ways of improving artillery and missile attacks.
Earlier this month, Shoigu's alleged ex-lover — and mother of two of his children — was exiled from Lithuania after being deemed a security threat, Lithuanian media reported.
Lithuania's State Security Department said this month that Yelena Shebunova's presence "may impose a threat to the country's national security over her links with Russian structures," Lithuanian National Radio and Television (LRT) reported.
It did not elaborate on why she was seen as a threat.
According to a 2019 investigation by Russian independent media outlet The Insider, Shebunova and Shoigu have two children together, both born out of wedlock: Daria and Danila.
It is unclear how old the children are, but The Insider reported that Shebunova obtained a Lithuanian residence permit in 2017.
In February, Shoigu told military officials the Russian army is "successfully" advancing near the eastern Ukrainian towns of Bakhmut and Vuhledar.
"Military operations are at the moment progressing with success in the areas around Vuhledar and Artemovsk," Shoigu told a defense meeting using the previous name for Bakhmut.