Cuba kicked off a crucial Communist Party congress Saturday with a massive military and civilian parade to mark 50 years since the defeat of CIA-backed exiles at the Bay of Pigs, still celebrated here as a landmark triumph over the island's powerful neighbor to the north.

Officials draped huge Cuban flags from government and other buildings; tanks rumbled down city streets and military planes roared through the skies. Cannon fire from Havana's seaside ramparts echoed periodically across the city.

Hundreds of thousands of people — from aging generals to factory workers — marched through the capital. Such shows of nationalism are one of the things Cuba does best, with participants given the day off and a fleet of Soviet-era buses mobilized to ferry them in from across the island.

The festivities on Saturday culminated at Revolution Plaza, a vast concrete expanse where an iconic sculpture of Ernesto "Che" Guevara gazes down from the side of the Interior Ministry building.

The Communist Party newspaper Granma reported that tens of thousands of young people would march at the rear of the parade, calling it a demonstration of the continuity of Fidel and Raul Castro's 1959 revolution.

Continuity is an important theme for Cuban leaders these days. President Raul Castro is 79 and his brother Fidel is 84.

Raul has acknowledged that this year's Communist Party gathering is likely to be the last overseen by the brothers and those who fought with them a half century ago. In speech after speech, he has lamented that the time the revolutionary generation has left is short, but the work needed to put Cuba's economy on track immense.

Since taking over the presidency permanently in 2008, Raul has turned over tens of thousands of hectares of fallow government land to small farmers, opened the economy to a limited amount of free enterprise, and gradually cut some of the generous health and food subsidies Cubans have come to expect from the state in return for working for extremely low wages.

He also has repeatedly warned Cubans that they must work harder if the island's moribund economy is to survive. Plans to lay off hundreds of thousands of state workers have been delayed indefinitely, but Raul has insisted they are still part of a larger five-year reform plan.

More details of that plan are expected to emerge from the four-day congress, which opens with a speech by Raul right after the parade. Many Cubans are hoping the congress will expand the list of approved private enterprises and relax rules on buying and selling homes and automobiles, among other measures.

The changes announced by Raul so far have already been a significant departure for a Marxist system where the government employs four-fifths of the work force and dominates nearly the entire economy.

Yet Castro has vowed the changes are meant to improve Cuba's socialist system, not toss it out.

It's no accident that the congress, the first since 1997, is being held on the anniversary of the Bay of Pigstriumph and Fidel Castro's April 16, 1961 announcement that the revolution would forever be socialist in nature.

"It sort of emphasizes where they've been and where they're going now," said Wayne Smith, a senior fellow at the Center for International Policy in Washington who was chief of the U.S. diplomatic mission on the island from 1979 to 1982. "It'll be very interesting to see what comes out of this congress. Just what kind of a new system are we going to see?"

In addition to the economic changes, delegates are expected to vote in new party leaders after Fidel Castro's announcement last month that he is no longer first secretary. With Raul all but certain to take up his brother's mantle, all eyes will be on who is named to the No. 2 spot — a graying revolutionary comrade, or a fresh new face.