Cuba

Shortly after arriving in Mexico in early September 1954, Guevara renewed his friendship with Ñico López and the other Cuban exiles whom he had known in Guatemala. In June, López introduced him to Raúl Castro. Some weeks later, Fidel Castro arrived in Mexico City after having been released from political prison in Cuba, and on the evening of 8 July 1955 Raúl introduced Guevara to him. During a fervid overnight conversation, Guevara became convinced that Castro was the inspirational revolutionary leader for whom he had been searching, and he immediately joined the "26th of July Movement" that intended to overthrow the government of Fulgencio Batista. Although it was planned that he would be the group's medic, Guevara participated in the military training along with the other members of the 26J Movement, and at the end of the course was singled out by their instructor, Col. Alberto Bayo, as his most outstanding student. Meanwhile, Gadea had arrived from Guatemala and she and Guevara resumed their relationship. In the summer of 1955 she informed him that she was pregnant and he immediately suggested that they marry. The wedding took place on August 18, 1955, and their daughter, whom they named Hilda Beatríz, was born on February 15, 1956.
When the cabin cruiser Granma set out from Tuxpan, Veracruz for Cuba on November 25, 1956, Guevara was the only non-Cuban aboard. Attacked by Batista's military soon after landing, about half of the expeditionaries were killed or executed upon capture. Guevara writes that it was during this confrontation that he laid down his knapsack containing medical supplies in order to pick up a box of ammunition dropped by a fleeing comrade, a moment which he later recalled as marking his transition from physician to combatant.Knapsack[›] Only 15–20 rebels survived as a battered fighting force; they re-grouped and fled into the mountains of the Sierra Maestra to wage guerrilla warfare against the Batista regime.
Guevara became a leader among the rebels, a Comandante (English translation: Major), respected by his comrades in arms for his courage and military prowess, and feared for what some have described as "ruthlessness": he was responsible for the execution of many men found guilty of being informers, deserters or spies. In the final days of December 1958, he directed the attack led by his "suicide squad" (which undertook the most dangerous tasks in the rebel army) on Santa Clara which was one of the decisive events of the revolution, although the bloody series of ambushes first during la ofensiva in the heights of the Sierra Maestra, then at Guisa, and the whole Cauto Plains campaign that followed probably had more military significance. Batista, upon learning that his generals — especially General Cantillo, who had visited Castro at the inactive sugar mill "Central America" — were negotiating a separate peace with the rebel leader, fled to the Dominican Republic on January 1, 1959.
On February 7, 1959, the victorious government proclaimed Guevara "a Cuban citizen by birth." Shortly thereafter, he initiated divorce proceedings to put a formal end to his marriage with Gadea, from whom he had been separated since before leaving Mexico on the Granma, and on June 2, 1959, he married Aleida March,Children[›] a Cuban-born member of the 26th of July movement with whom he had been living since late 1958.

TIME magazine, August 8, 1960
He was appointed commander of the La Cabaña Fortress prison, and during his six-month tenure in that post (January 2 through June 12, 1959), he oversaw the trial and execution of many people including former Batista regime officials, members of the BRAC (Buró de Represión de Actividades Comunistas, "Bureau for the Repression of Communist Activities") secret police, alleged war criminals, and political dissidents. The trials he conducted were alleged to be "unfair", according to Time Magazine. Later, Guevara became an official at the National Institute of Agrarian Reform,INRA[›] and President of the National Bank of CubaBNC[›] (somewhat ironically, as he often condemned money, favored its abolition, and showed his disdain by signing Cuban banknotes with his nickname, "Che").
During this time his fondness for chess was rekindled, and he attended and participated in most national and international tournaments held in Cuba. He was particularly eager to encourage young Cubans to take up the game, and organized various activities designed to stimulate their interest in it.
Even as early as 1959, Guevara helped organize revolutionary expeditions overseas, all of which failed. The first attempt was made in Panama; another in the Dominican Republic (led by Henry Fuerte, also known as "El Argelino", and Enrique Jiménez Moya) took place on 14 June of that same year.

Che Guevara with Fidel Castro (Havana - April 1961)
In 1960 Guevara provided first aid to victims during the La Coubre arms shipment rescue operation that went further awry when a second explosion occurred, resulting in well over a hundred dead. It was at the memorial service for the victims of this explosion that Alberto Korda took the most famous photograph of him. Whether La Coubre was sabotaged or merely exploded by accident is not clear. Those who favour the sabotage theory sometimes attribute this to the Central Intelligence Agency and sometimes name William Alexander Morgan, a former rival of Guevara's in the anti-Batista forces of the central provinces and later a putative CIA agent, as the perpetrator. Cuban exiles have put forth the theory that it was done by Guevara's USSR-loyalist rivals.
Guevara later served as Minister of Industries,MININD[›] in which post he helped formulate Cuban socialism, and became one of the country's most prominent figures. In his book Guerrilla Warfare, he advocated replicating the Cuban model of revolution initiated by a small group (foco) of guerrillas without the need for broad organizations to precede armed insurrection. His essay El socialismo y el hombre en Cuba (1965) (Man and Socialism in Cuba) advocates the need to shape a "new man" (hombre nuevo) in conjunction with a socialist state. Some saw Guevara as the simultaneously glamorous and austere model of that "new man."
During the 1961 Bay of Pigs Invasion, Guevara did not participate in the fighting, having been ordered by Castro to a command post in Cuba's westernmost Pinar del Río province where he was involved in fending off a decoy force. He did, however, suffer a bullet wound to the face during this deployment, which he said had been caused by the accidental firing of his own gun.

Guevara played a key role in bringing to Cuba the Soviet nuclear-armed ballistic missiles that precipitated the Cuban Missile Crisis in October 1962. During an interview with the British newspaper Daily Worker some months later, he stated that, if the missiles had been under Cuban control, they would have fired them against major U.S. cities.