For half a century his existence has mocked the superpower that tried to kill, topple and isolate him. Fidel Castro seemed immortal, and there was nothing the US could do about it.

US presidents came and went, the Berlin Wall fell, Cuba tottered and Castro, ambushed by illness, relinquished power. But still he resisted the “biological solution” – a Washington euphemism for Castro’s death. He clung to life, to defiance, and surfaced every so often to assail the capitalist enemy.

On Tuesday the “maximum leader” emerged into the limelight again but this time there was no thunder. It was, apparently, goodbye. “I’ll be 90 years old soon,” Castro told the Communist party in a valedictory speech at the closure of its four-day congress in Havana. “Soon I’ll be like all the others.”

After decades of revolutionary fervour in marathon speeches and newspaper columns it was time, in an occasionally trembling voice, for a hint of elegy.

“The time will come for all of us, but the ideas of the Cuban communists will remain as proof on this planet that if they are worked at with fervour and dignity, they can produce the material and cultural goods that human beings need, and we need to fight without truce to obtain them.”

State television, in a delayed, edited broadcast, showed the former president, wearing a plaid shirt and sports top, seated at the dais in the convention palace, consulting notes as he spoke. Party members responded with shouts of “Fidel!”

Who could have guessed that the olive-uniformed rebel who overthrew Fulgencio Batista in 1959, who inspired and alienated generations of leftwingers, who flirted with nuclear armageddon during the 1962 missile crisis, who outlasted the Soviet Union and 10 US presidents, would make it to 2016, almost a nonagenarian, bowing to Father Time?

Cuba’s Communist party, however, is not bowing to economic difficulties or ideological pressure despite restored diplomatic ties with the US.

The seventh party congress announced that Fidel’s brother Raúl, who succeeded him in 2008, will retain the party’s highest post alongside his hardline second-in-command. State media said Raúl, 84, would remain the party’s first secretary and José Ramón Machado Ventura would hold the post of second secretary for at least part of a second five-year term.

Raúl is both president and first secretary. The decision means he could hold a party position at least as powerful as the presidency even after stepping down from the government post in 2018.

Machado Ventura, 85, is known as an enforcer of communist orthodoxy who has resisted cautious efforts to reform the island’s moribund, centrally planned economy. Even high-ranking government officials had speculated a young reformer would succeed him.

The party congress also decided against shaking up the powerful 15-member political bureau. It appointed five new members, none of whom were high-profile advocates for reform.

Speaking at the congress closure, Raúl said it would be the last one headed by current leaders, signalling a generational transition in the next five years. “This seventh congress will be the last one led by the historic generation.”