Cuba became a communist state because Cuban leader Fidel Castro believed communism was the movement of the working class. Castro also established strong ties with the Soviet Union, and sharing its communist ideals ensured military and financial support from the Russians.
Castro rose to power in 1959, leading the revolution to overthrow dictator Fulgencio Batista. Batista was a former army sergeant who ran for president of Cuba in 1952. When his defeat seemed inevitable, the elections were canceled, and Batista seized power. Many Cubans disapproved of this power grab, including Fidel Castro, who was an aspiring politician at the time. As the Batista regime became more corrupt, brutal and inefficient, support for the revolution increased. The United States government supported Batista who it believed would be more protective of American interests in Cuba than the revolutionaries.
Castro and a group of supporters including Che Guevara eventually succeeded in ousting Batista in 1959. While the Cuban revolution is associated with communism, it was not a driving force behind the uprising. Castro did not declare himself a communist until 1961 when he stated publicly that he was a Marxist-Leninist. This statement strengthened Cuba's diplomatic relations with the Soviet Union and led to an increasingly strained relationship with the United States.