Jair Bolsonaro always swore he would never be imprisoned.

This trademark defiance crumbled as the man who rose from fringe firebrand to president and reshaped Brazilian politics began serving a 27-year sentence for a failed coup bid.

Bolsonaro, a former army captain, once electrified supporters with his gloves-off style, while drawing criticism for comments slamming gays, demeaning women and praising Brazil's dictatorship years.

The 70-year-old cut a far more subdued figure as he began his sentence, with warnings from his family over his "extremely fragile" mental and physical health.

Just days earlier, Bolsonaro claimed a medication-induced bout of paranoia led him to try to sever his ankle monitoring bracelet with a soldering iron while under house arrest.

The Supreme Court saw this as an attempt to escape his imminent imprisonment.

Bolsonaro was convicted in September over a scheme to prevent President Luiz Inacio Lula da Silva from taking power after he lost a re-election bid in 2022.

Judges found that the plot -- which included plans to assassinate Lula -- only failed because it did not have enough support from military top brass.

Bolsonaro maintains his innocence, claiming he is the victim of political persecution.

When he ran for re-election in 2022, Bolsonaro said there were three potential outcomes for his future: "Prison, death or victory."

The prison option however, "does not exist," he said.

"By God who is in heaven, I will never be imprisoned," he said that same year.

Bolsonaro has, however, managed to escape a traditional jail cell and will serve his sentence in a special room at police headquarters equipped with a TV, mini-fridge, and air-conditioning.

- 'Bibles, bullets and beef' -

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Bolsonaro, a longtime congressman, won the presidency amid wide-ranging disgust over corruption scandals that had engulfed leftist governments / © AFP

Bolsonaro was a longtime congressman when he managed to seize a crucial political moment in Brazil in 2018 elections: wide-ranging disgust over a series of corruption scandals that had engulfed leftist governments.

His diatribes against the "rotten" left and fiery remarks about homosexuality and the role of women won him the support of Brazil's powerful so-called "Bibles, bullets and beef" electorate -- evangelical Christians, security hardliners and the agribusiness industry.

Bolsonaro, who was in office from 2019-2022, was often compared to his ally US President Donald Trump, who called the trial a "witch hunt" and punished Brazil with sanctions and trade tariffs.

However, Bolsonaro's influence with Trump waned in recent months as Lula cosied up to the US leader, who agreed to drop some tariffs.

In 2018, Bolsonaro survived a knife attack while campaigning that left him with severe abdominal wounds that continue to plague him.

He also suffers from "uncontrollable hiccups" that have left him out of breath and fainting, according to his doctors.

His lawyers warn prison poses a risk to his life.

- Amazon fires and Covid denial-

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Jair Bolsonaro has battled health issues and his lawyers argue that sending him to prison would pose a risk to his life / © AFP/File

Born in 1955 to a Catholic family with Italian roots, Bolsonaro served in the army before launching his political career in the late 1980s as a Rio de Janeiro city councilor.

In 1991, he was elected to Congress.

He quickly became known for his incendiary comments claiming he was in favor of dictatorship and defending torture.

In 2011, he told Playboy magazine he would rather his sons be killed in an accident than come out as gay.

Three years later, he said a left-wing lawmaker was "not worth raping" because she was "too ugly."

Bolsonaro drew international criticism as fires and deforestation in the Amazon rainforest spiked under his leadership and as he weakened environmental agencies.

When Covid-19 hit, he downplayed it as a "little flu" and expressed skepticism about vaccines -- joking those who took them might "turn into a crocodile" -- while promoting unproven treatments.

Twice divorced, Bolsonaro married his current wife Michelle, a fervent Evangelical Christian 27 years his junior, in 2007.

He reversed a vasectomy to have a child with Michelle and once described fathering his daughter Laura as a "moment of weakness" after having sired four sons in previous marriages.

Three of his sons are politicians.