With no time to consult Castro, former guerrilla journalist Carlos Franqui, a member of Castro's July 26 Movement directorate and head of Radio Rebelde, took to the airwaves.
Messengers ran to tell Castro, who was positioned in a sugar mill some 40 miles north of Santiago.
''I had to start making decisions that were the directorate's or Fidel's to make,'' said Franqui, who left Cuba in 1968 and now lives in Puerto Rico. ``It would have been fatal for Radio Rebelde to have been silent. I decided to take responsibility and make logical decisions.''
Batista had fled, but the guerrilla war was not won.
Gen. Cantillo was busy in Havana finding a senior magistrate to take Batista's place, as the constitution dictated. Cantillo enlisted an unwilling judge in his bathrobe.
Castro wanted to fill the power vacuum himself. Furious and fearful that the rebels would be shut out, he started barking orders.
''Naturally the first of January was also a terrible day,'' Castro said in Franqui's 1976 book, Diary of the Cuban Revolution. ``We were betrayed, and an attempt was made to snatch victory from the people. We had to act very swiftly.''
Castro hustled to the eastern town of Palma Soriana to record radio broadcasts.
Guerrilla commander Camilo Cienfuegos went to Camp Columbia near Havana, while Raúl Castro was sent to force Guantánamo's surrender. Guevara was dispatched to the La Cabaña fortress in Havana harbor.
''Revolution, yes!'' Castro proclaimed over the airwaves. ``Military coup, no!''
''It was a plan that was made and executed with such precision that Batista fell practically on the day we thought he would fall, and Santiago de Cuba was taken more or less on the day that we thought we would take it,'' Castro said in the 1976 book.
``They attempted to snatch the triumph from us, and if there hadn't been swift action, the consequences would have been serious.''
Some people in Havana acted fast, too: Jubilant crowds looted casinos and ransacked the homes of Batista loyalists.
''I could see people running carrying drapes, lamps, air conditioners,'' Fabricio, then 12, recalled watching from his apartment building across the Riviera Hotel on Havana's famed seawall. ``They took doors off the hinges. The other unpopular part of the regime was the parking meters, and people were taking bats to them.''
Brothers to the Rescue founder José Basulto, then 18 and heading off for college, remembers people preparing Molotov cocktails at the long-shuttered University of Havana while slot machines tumbled down city streets.
'There was an atmosphere of trouble. Everybody was thinking: `What's next?' '' Basulto said. ``I remember that I walked into a police station and took a gun for myself. The police were there, looking at us. They were on the job, but not acting on it.''
Matos' attack on Santiago never materialized, as military leaders easily gave in. Raúl Castro took Moncada barracks without firing a shot.
That evening, Castro declared victory from the balcony of Santiago de Cuba's City Hall. Franqui remembers the throngs of thousands who rushed to greet Castro and touch his scraggly beard.
''It was a bit cultish,'' Franqui said. ``It disgusted me.''
With lawyer Manuel Urrutia named president, Castro began a weeklong trek to Havana, where he was greeted like a messiah. He did not arrive until Jan. 8, and did not officially appoint himself to the top job for another 45 days.
''I don't remember anyone who was unhappy, or sad, or concerned about what had just happened. It was just the opposite,'' remembers Miami Dade College President Eduardo Padrón, who was 14. ``On that date, Jan. 1, we really did not imagine the whole magnitude of what would transpire years to come. At that moment, it did not occur to us that this would turn into something we would dislike or actually hate or that it would last this long.
``Fifty years is a long, long time.''