By Jeff Franks
HAVANA (Reuters) - Cuba readied for a Communist Party congress about its future with a tribute to the past on Saturday, staging a military parade for the 50th anniversaries of the U.S.-backed Bay of Pigs invasion and the declaration of Cuban socialism.
Troops marched through Havana and fighter jets roared across the sky to mark the two watershed events that will be followed by another later in the day when the ruling Communists begin a four-day congress.
President Raul Castro says the future of Cuban socialism put in place after the island's 1959 revolution is at stake.
The congress of Cuba's highest political body is expected to introduce possible new leaders and approve wide-ranging reforms to an economy Castro has said is on the brink of failure.
The military parade was all pride and patriotism as hundreds of soldiers marched through Revolution Square where Castro, 79, and an array of dignitaries looked on.
The troops were followed by hundreds of thousands of flag-waving civilians in the carefully orchestrated event.
Former leader Fidel Castro, 84 and ailing, did not attend, but his name was invoked often by parade participants.
As refurbished military vehicles with rocket launchers and mortars passed by and a small fleet of helicopters flew overhead, followed by five streaking Soviet MiGs, a parade announcer declared the materiel "modernized and ready to confront any imperialist aggression."
It was Fidel Castro who, on April 16, 1961, fearing U.S. invasion was imminent, finally told Cubans what the 1959 revolution he led from the Sierra Maestra mountains was all about.
"What the imperialists can't forgive us ... is that we have made a socialist revolution right under the nose of the United States," he proclaimed in speech paying tribute to victims of pre-invasion bombing raids the previous day.
On April 17, a force of CIA-trained Cuban exiles, backed by U.S. ships and planes, came ashore at the Bay of Pigs 100 miles southeast of Havana in a bloody attempt to spark a counter-revolution.
Castro rallied tens of thousands of troops and citizens to the battle and two days later declared victory as the attackers fled or were killed or captured in the botched invasion.
The triumph by tiny Cuba versus the superpower 90 miles away won Castro favor at home and abroad and is portrayed by Cuban leaders as one of their greatest accomplishments.
The socialist state Fidel Castro created has survived despite continuing U.S. opposition, but it is so tattered that Raul Castro says it must be fixed in order to survive.
Because of that and the possible glimpse of new leadership it may provide, this 6th party congress is considered the most important since the first in 1975, where Cuba adopted a Soviet-style system.
The 1,000 delegates will give their blessing to all or part of a package of nearly 300 reforms that Raul Castro says will put socialism on solid footing for the future.
They are expected to elect him as First Secretary, to replace Fidel Castro, who revealed last month he resigned the post when he fell seriously ill in 2006.
Closely watched for any signs of new blood will be the selections for Second Secretary, the post Raul Castro has held, and for the Central Committee and Political Bureau.
Due to the "laws of life," this is likely the last party congress for Cuba's aging leaders, President Castro has said.
The leaders emerging from this congress will preside over an economic transition that will reduce the size of the state and expand the private sector, while maintaining central planning.
Many of the changes are already in place, including a program to slash more than a million jobs from state payrolls, cut subsidies and allow more self-employment.
(Additional reporting by Rosa Tania Valdes and Nelson Acosta; Editing by Jackie Frank)