structural:scholar_edition
Escalation and U.S. involvement

The United States supplied Cuba with planes, ships, tanks, and other technology such as napalm, which was used against the rebels. This would eventually come to an end due to a later arms embargo in 1958. On the other side, the Cuban rebels were supplied by Yugoslavia under Josip Broz Tito.

According to Tad Szulc, the United States began funding the 26th of July Movement around October or November 1957 and ending around middle 1958. "No less than $50,000" would be delivered to key leaders of the 26th of July Movement, the purpose being to instill sympathies to the United States amongst the rebels in case the movement succeeded.

While Batista increased troop deployments to the Sierra Maestra region to crush the 26 July guerrillas, the Second National Front of the Escambray kept battalions of the Constitutional Army tied up in the Escambray Mountains region. The Second National Front was led by former Revolutionary Directorate member Eloy Gutiérrez Menoyo and the "Comandante Yanqui" William Alexander Morgan. Gutiérrez Menoyo formed and headed the guerrilla band after news had broken out about Castro's landing in the Sierra Maestra, and José Antonio Echeverría had stormed the Havana Radio station. Though Morgan was dishonorably discharged from the U.S. Army, his recreating features from Army basic training made a critical difference in the Second National Front troops' battle readiness.

Thereafter, the United States imposed an economic embargo on the Cuban government and recalled its ambassador, weakening the government's mandate further. Batista's support among Cubans began to fade, with former supporters either joining the revolutionaries or distancing themselves from Batista. Once Batista started making drastic decisions concerning Cuba's economy, he began to nationalize U.S. oil refineries and other U.S. properties.

Batista's government often resorted to brutal methods to keep Cuba's cities under control. However, in the Sierra Maestra mountains, Castro, aided by Frank País, Ramos Latour, Huber Matos, and many others, staged successful attacks on small garrisons of Batista's troops. Castro was joined by CIA connected Frank Sturgis who offered to train Castro's troops in guerrilla warfare. Castro accepted the offer, but he also had an immediate need for guns and ammunition, so Sturgis became a gunrunner. Sturgis purchased boatloads of weapons and ammunition from CIA weapons expert Samuel Cummings' International Armament Corporation in Alexandria, Virginia. Sturgis opened a training camp in the Sierra Maestra mountains, where he taught Che Guevara and other 26 July Movement rebel soldiers guerrilla warfare.

In addition, poorly armed irregulars known as escopeteros harassed Batista's forces in the forests and mountains of Oriente Province. The escopeteros also provided direct military support to Castro's main forces by protecting supply lines and by sharing intelligence. Ultimately, the mountains came under Castro's control.

In addition to armed resistance, the rebels sought to use propaganda to their advantage. A pirate radio station called Radio Rebelde ("Rebel Radio") was set up in February 1958, allowing Castro and his forces to broadcast their message nationwide within enemy territory. Castro's affiliation with the New York Times journalist Herbert Matthews created a front page-worthy report on anti-communist propaganda. The radio broadcasts were made possible by Carlos Franqui, a previous acquaintance of Castro who subsequently became a Cuban exile in Puerto Rico.

During this time, Castro's forces remained quite small in numbers, sometimes fewer than 200 men, while the Cuban military and police force had a manpower of around 37,000. Even so, nearly every time the Cuban military fought against the revolutionaries, the army was forced to retreat. An arms embargo – imposed on the Cuban government by the United States on 14 March 1958 – contributed significantly to the weakness of Batista's forces. The Cuban air force rapidly deteriorated: it could not repair its airplanes without importing parts from the United States.