At 3:00 a.m. he wakes the troops up and organizes the groups for action. The Moncada manifesto written under the guidance of Fidel by Raúl Gómez García and the poem "Ya estamos en Combate" (We are ready for combat). They sing the National Anthem.

At 4:45 a.m. the fighters leave in 16 cars towards the city with the Moncada Barracks, the Civil Hospital "Saturnino Lora" and the Palace of Justice as targets to be taken.

At 5:15 a.m. The attacks to the Moncada barracks in Santiago de Cuba and Carlos Manuel de Céspedes in Bayamo begin simultaneously.

The action, planned as the trigger for a popular uprising against the Batista dictatorship, fails from the military point of view due to fortuitous reasons but constitutes a great political blow to the tyranny and a mobilizing factor of the people for the struggle. Many of the assailants are taken prisoner by forces of the dictatorship and later assassinated.

Faced with the failure of the operation, Fidel orders the retreat to the Siboney Farm where some 36 fighters meet.

Along with 18 of the survivors, they go to the mountains through the area of ​​the La Gran Piedra (Great Rock), divided into subgroups, to continue the armed struggle

He receives in his prison cell of Isle of Pines the unexpected visit of the then Minister of the Interior, Ramón O. Hermida, who comes to apologize after having publicly insulted Fidel.

After the visit, a crisis arises in the Batista cabinet, as Rafael Díaz-Balart scorns Hermida in a public letter. Both resign and Batista intervenes to appease the issue.

He commemorates the second anniversary of the Attack on the Moncada Barracks in the Mexican capital. In the morning he lays a floral tribute at the Monument to the Child Heroes of Chapultepec, and at night, he speaks in an event, at the Spanish Athenaeum, sponsored by the Latin American exiles, where he highlights the revolutionary significance of Puerto Rican independence fighter Pedro Albizu Campos, among other topics.