Raúl Castro has spent most of his life in his brother’s shadow, but he has proved a more than capable successor as Cuban president.

A cautious pragmatist to Fidel’s charismatic ideologue, many felt the younger sibling was a mere stopgap when he formally assumed power in 2008.

But he has subsequently made his own very distinctive mark on the island’s history with a program of economic reforms, an easing of travel restrictions and the restoration of diplomatic relations with the United States.

The death of Fidel and the looming presidency of Donald Trump, whose Cuban policy remains unclear, are uncharted waters which will test Raúl’s nerve and judgment as never before.

On Monday, Trump threatened to reimpose sanctions on Cuba, but gave no details or explanation.

Some analysts said they did not expect Trump to rescind the executive orders that relaxed the half-century embargo on Cuba since Castro came to power, citing the pro-business lobby in the Republican party and Trump’s own commercial instincts.

However, conservative Cuban Americans – including Mauricio Claver-Carone, a hardline member of Trump’s transition team – have said that the regime run by Raúl Castro is just as repressive as his brother’s, and argue that some or all of the sanctions should be reinstated.

Since taking the helm Raúl has cemented his own personal power, maintained the hegemony of the Communist party and laid to rest the once widely held belief that Cuba would implode with the death of Fidel.

“Raúl is a transitional president between the old guard and the future and in that sense he has performed well. He has kept the country stable,” said Volker Skierka, a Fidel biographer and Cuba expert.

Raúl Castro with his brother Fidel, left, and Che Guevara, right. Photograph: Giovannetti/IPA/Rex/Shutterstock

Like his brother, he has also ensured this small island maintained a disproportionate amount of global attention. Groundbreaking visits to Havana by Barack Obama and Pope Francis made headlines around the world and drove home the message that Cuba was changing – albeit on its own terms. Under Raúl’s leadership, Cuba also hosted peace talks between the Colombian government and Farc insurgents that may end the bloodiest conflict in Latin America.

In his later years, Fidel expressed his unease with some of these developments in critical commentaries in Granma, the Communist party newspaper, but his influence was waning and what was left of the revolution had already moved on.

US policymakers have been forced to abandon their once cherished “poof moment” theory that the communist party’s grip on power would slip without Fidel. “As much as we wish otherwise, I don’t see it happening,” said one US diplomat in the region.

European diplomats went further. “We won’t see a huge shift of Cuban politics after Fidel’s death. More significant would be if Raúl dies, because he put his leadership on the line for reform.”

Marginalised and intimidated dissidents pose little threat to the government. They resonate internationally as symbols of opposition but foreign diplomats in Havana write them off as politically irrelevant on the island.

Raúl has released most political prisoners and allowed prominent critics such as Rosa María Payá and Yoani Sánchez to travel abroad. But organised opposition at home is still often met with arrests and beatings.

Raúl’s biggest test is raising living standards for the island’s 11.2 million people. The average monthly wage is less than £15 ($20), obliging people to scrabble for decent food and basics such as soap, and there are crippling shortages of housing and transport.

“The economy is what’s most on people’s minds,” said Susan Kaufman Purcell, director of the Centre for Hemispheric Policy at the University of Miami.

Raúl has studied Vietnam and China as models of communist parties which have retained control while freeing their economies. He has trimmed the vast state bureaucracy and laid off hundreds of thousands of workers, saying the old system was bloated and unsustainable.

Raúl Castro has laid to rest the belief that Cuba would implode with the death of Fidel, but his biggest challenge will be to raise living standards. Photograph: Yamil Lage/AFP/Getty Images

To soak up these workers and create opportunities for the young, he has encouraged personal initiative and licensed hundreds of different types of micro-businesses. He has told Cubans to stop blaming the US embargo for their ills and to be “fearless” in criticising corruption, bureaucracy and inefficiency.

The reforms have allowed small new businesses to bloom, notably restaurants, guesthouses and stalls which have livened up Havana’s sleepy streets, but efforts to boost agriculture have fallen flat, with farmers complaining of multiple obstacles. Shortages of basic foodstuffs remain the norm for most Cubans.

The challenge is to deliver material improvements while retaining the free and universal access to education and healthcare that are the revolution’s proudest boast and main pillar of legitimacy.

In contrast to Fidel’s marathon speeches and nocturnal workaholic habits, Raúl is a family man who speaks briefly and likes to be home for dinner. He delegates decisions to a small, trusted cabal. Raúl’s power base is the military, an institution he forged during 47 years as defence minister.

For the past decade, Venezuelan oil subsidies have been crucial to Cuba’s economy. President Nicolás Maduro, who succeeded the Fidel-worshipping Hugo Chávez, is close to Raúl. With the aid of Cuba’s G2 intelligence service he keeps close tabs on Venezuela, whose economy is collapsing. Should Maduro fall, alarm bells will sound across Havana.

Cuba learned the hard way not to become too dependent on a single sponsor. In the 1990s, after the collapse of the Soviet Union, the island’s economy was in tatters and many of its citizens struggled to feed themselves. Ever the pragmatist, Raúl has spent his years as president hedging against this possibility by nurturing ties with China, Russia, Latin America, the European Union and even the US.

But nobody should mistake that for a shift of ideology. In his 2016 speech to the party congress, Raúl echoed his brother’s calls for unity in the face of capitalist US influence.

Under Raúl’s leadership relations between the US and Cuba have warmed, marked by Barack Obama’s historic visit. Photograph: Ramon Espinosa/AP

“If one day they manage to fragment us, that would be the beginning of the end of the revolution, of socialism and independence in our homeland,” he said.

Raúl’s other outstanding task is grooming a successor. He has repeatedly insisted a generational change is long overdue, most recently at the 2016 Communist party congress when he said nobody should be over the age of 60 when they join the country’s top decision-making body.

But for the moment, his inner circle is dominated by octogenarians. One reason for the hesitancy is younger colleagues lack the cachet of involvement in the 1959 revolution that overthrew the Batista dictatorship, another pillar of legitimacy. Without that whiff of history they are just unelected officials.

Nonetheless, the Cuban president has said he will stand down as president in 2018 and his first vice-president, Miguel Díaz-Canel, is widely tipped to assume his mantle. Fidel’s death – expected to be more of an emotional than political earthquake for Cuba – is unlikely to change that, but it could make change easier for the next generation of Cuban leaders.

Additional reporting by Julian Borger