MOSCOW - A KGB officer turned world leader, Vladimir Putin has stamped his total authority on Russia, silencing opposition and reasserting Moscow's lost might abroad while building a strongman image through macho stunts.

Putin, 65, who will be inaugurated as president for the fourth time on Monday, has reimposed the Kremlin's grip on society since taking power 18 years ago after a lawless but relatively free decade following the demise of the USSR.

On the international stage, he has dealt with three US presidents, thrust Moscow into a new rivalry with the West by snatching Crimea from Ukraine and launched a pivotal intervention in Syria.

Named the world's most powerful person by Forbes for the past 4 years running, the judo black belt has carefully nurtured his image as a powerful leader with photo opportunities showing him riding topless on horseback in the Siberian wilderness and darting an endangered tiger.

Supporters laud him as a savior who restored pride and traditional values to a humiliated nation.

To foes, however, Putin has dragged his homeland further from democracy, presided over a seizure of the state by a new elite of former secret police cronies and stoked nationalism in a bid to restore Moscow's lost empire.

'HIT LIST'

Putin was born into a working-class family in Leningrad -- now Saint Petersburg -- on October 7, 1952 and cut his teeth in the city's rough-and-tumble neighborhoods.

"The Leningrad streets taught me one thing: if a fight is unavoidable, you have to hit first," Putin said in 2015.

He fulfilled a childhood dream by joining the KGB intelligence service, with a posting in 1985-1990 in Dresden -- then East Germany -- just as Soviet power was crumbling.

His political rise began after he returned to work at Saint Petersburg city hall under his mentor, liberal mayor Anatoly Sobchak.

By 1996, he was called to Moscow to work in the Kremlin under Russia's first democratically elected president Boris Yeltsin, who in 1998 made little-known Putin head of the KGB's successor, the FSB.

Battling health and drinking problems, frail Yeltsin in August 1999 named Putin prime minister and his popularity shot up as he oversaw the launch of a second war to crush rebels in the Chechnya region.

When Yeltsin sensationally resigned on New Year's Eve 1999, Putin took over as president of the biggest country on Earth.

A TSAR IS BORN

Buoyed by an influx of petrodollars that saw living standards soar, the Kremlin under Putin forged its own "sovereign democracy" in which the trappings of pluralism -- such as political opposition and civil society -- were subverted.

He has guarded his private life jealously and once famously told journalists to keep their "snotty noses" out of his business.

After three decades of marriage, he divorced his wife Lyudmila in 2013 but rumors of new romance -- including with a former Olympic gymnast -- have not been confirmed.

In line with the constitution, when Putin ended his second term in 2008, he handed power to protege Dmitry Medvedev and moved to become prime minister -- but few doubted who was really in charge.

In 2012, he returned as president in the face of huge street protests.

While the demonstrations petered out after a police crackdown, the spectre of unrest spurred tough new measures to eradicate dissent.

CRIMEA, UKRAINE, SYRIA

Putin, who once decried the collapse of the USSR as the "greatest geopolitical catastrophe" of the 20th century, has ferociously defended Moscow's sphere of influence and also challenged perceived US hegemony.

When crowds in Ukraine ousted Russia-backed leader Viktor Yanukovych in February 2014, the Kremlin faced losing its dominance over a key neighbour.

Within days, Putin ordered special forces to seize the strategic Crimea peninsula and -- after a hasty referendum rejected internationally -- in March 2014 signed off on the region's annexation.

The redrawing of Russia's border sparked the worst standoff with the West since the Cold War and unleashed a wave of nationalism at home that saw Putin's popularity soar.

Soon the Kremlin was accused of masterminding a rebellion in east Ukraine that turned into a festering conflict that has cost more than 10,000 lives.

Despite sanctions pushing the economy into recession, Putin also launched a bombing campaign in Syria to support leader Bashar al-Assad in 2015. It is widely seen as the key factor that tipped the war in Assad's favor.

Putin was then accused of spreading his tentacles much further and Moscow's old foe -- the United States -- found itself in the crosshairs.

After Donald Trump's shock election win, US intelligence accused Putin of ordering a hacking and influence campaign to get Trump to the White House.

"Those that lose always look to blame someone else," Putin retorted.

© Agence France-Presse