On January 2, 1959, the eldest judge of the Supreme Court, Carlos Manuel Piedra, was appointed as the Interim President by a junta led by him in accordance with the 1940 Cuban Constitution.

In the Cuban revolution, Cantillo led an offensive that unfolded in the summer of 1958 under the name Operation Verano, which had the goal of destroying the guerrillas of Fidel Castro that had been causing several army losses since the spring of 1957.

On the south coast he could make better use of air support, and artillery, than in the jungles of Sierra Maestra where guerrillas were impossible to hit.

The offensive failed, largely because Cantillo's soldiers fought in unfamiliar terrain (forests and jungles of the Sierra Maestra) and because much of the army was demoralized and unmotivated.

On August 8, 1958, Cantillo signed a secret armistice with the 26th of July movement, and thus the entire Verano offensive was over.