Fidel Castro was the last of a generation of revolutionary leaders whose Cold War confrontations with the United States and alliances with the Soviet Union defined the second half of the 20th century.
For decades after he led the Cuban revolution in 1959, Castro personified a third world socialist movement that saw him as lionised in Moscow as he was castigated in Washington.
Mikhail Gorbachev, the last leader of the Soviet Union on Saturday hailed Fidel Castro for "strengthening" his island nation.
"Fidel stood up and strengthened his country during the harshest American blockade, when there was colossal pressure on him and he still took his country out of this blockade to a path of independent development," Interfax news agency quoted Gorbachev as saying.
"In the past years, even when Fidel Castro was not formally in power, his role in strengthening the country was huge."
Gorbachev added that Castro would be remembered as a "prominent politician" who managed to leave a "deep mark in the history of mankind."
Vladimir Putin praised the Cuban revolutionary as a "symbol of an era", the Kremlin said.
Their words hark back to what was one of the most important and controversial alliances of the 20th century.
The brand of third world socialism that Castro championed was adopted by a series of post-Second World War regimes.
Castro's confrontation with the US started early, when John F Kennedy's administration authorised a botched invasion by Cuban exiles at the Bay of Pigs in 1961.
He quickly became a Soviet ally and, two years later, allowed Moscow to base nuclear missiles on the island, sparking a crisis that took the world to the bring of nuclear war.
Over the next several decades he defied - with considerable Soviet economic assistance - an American economic blockade and sent troops to fight in other revolutionary wars in Latin America and Africa.
Che Guevara, the Argentinian revolutionary who fought with Castro during the Cuban revolution, was killed on one of those expeditions in Bolivia in 1967.
All that changed in 1991, however, when the Soviet Union collapsed and Moscow abandoned both socialist ideology and its costly Cold War era alliances.
The evaporation of Soviet financial aid dealt the island's economy a heavy blow and led to some resentment in Havana over Moscow's apparent betrayal. But while communist regimes across eastern Europe collapsed, Castro refused to give up on revolutionary socialism.
Even when elites in surviving communist regimes in China and Vietnam embraced the benefits of globalisation, Castro refused to change his green army fatigues for a suit.
For socialists in both the west and the east, he became a rare living link to an era when socialist revolution was not only achievable, but seemed like it might well achieve its goal of transforming the world.
But unlike other revolutionary heroes like Lenin, Mao, and Ho Chi Minh, Castro will not be preserved as a museum piece. President Raul Castro, who took power after the revolutionary leader was admitted to hospital in 2006, said his elder brother's remains would be cremated early on Saturday.