information:extraction
Visit to Algeria and political turn

In Algiers, Algeria, on 24 February 1965, Guevara made what turned out to be his last public appearance on the international stage when he delivered a speech at an economic seminar on Afro-Asian solidarity. He specified the moral duty of the socialist countries, accusing them of tacit complicity with the exploiting Western countries. He proceeded to outline a number of measures which he said the communist bloc countries must implement in order to accomplish the defeat of imperialism. Having criticized the Soviet Union (the primary financial backer of Cuba) in such a public manner, he returned to Cuba on 14 March to a solemn reception by Fidel and Raúl Castro, Osvaldo Dorticós, and Carlos Rafael Rodríguez at the Havana airport.

As revealed in his last public speech in Algiers, Guevara had come to view the Northern Hemisphere, led by the US in the West and the Soviet Union in the East, as the exploiter of the Southern Hemisphere. He strongly supported communist North Vietnam in the Vietnam War, and urged the peoples of other developing countries to take up arms and create "many Vietnams". Che's denunciations of the Soviets made him popular among intellectuals and artists of the Western European left who had lost faith in the Soviet Union, while his condemnation of imperialism and call to revolution inspired young radical students in the United States, who were impatient for societal change.

Marx characterized the psychological or philosophical manifestation of capitalist social relations as alienation and antagonism; the result of the commodification of labor and the operation of the law of value. For Guevara, the challenge was to replace the individuals' alienation from the productive process, and the antagonism generated by class relations, with integration and solidarity, developing a collective attitude to production and the concept of work as a social duty.

—Helen Yaffe, author of Che Guevara: The Economics of Revolution

In Guevara's private writings from this time (since released), he displays his growing criticism of the Soviet political economy, believing that the Soviets had "forgotten Marx ". This led Guevara to denounce a range of Soviet practices including what he saw as their attempt to "air-brush the inherent violence of class struggle integral to the transition from capitalism to socialism", their "dangerous" policy of peaceful co-existence with the United States, their failure to push for a "change in consciousness" towards the idea of work, and their attempt to " liberalize " the socialist economy. Guevara wanted the complete elimination of money, interest, commodity production, the market economy, and " mercantile relationships ": all conditions that the Soviets argued would only disappear when world communism was achieved. Disagreeing with this incrementalist approach, Guevara criticized the Soviet Manual of Political Economy, predicting that if the Soviet Union did not abolish the law of value (as Guevara desired), it would eventually return to capitalism.

Two weeks after his Algiers speech and his return to Cuba, Guevara dropped out of public life and then vanished altogether. His whereabouts were a great mystery in Cuba, as he was generally regarded as second in power to Castro himself. His disappearance was variously attributed to the failure of the Cuban industrialization scheme he had advocated while minister of industries, to pressure exerted on Castro by Soviet officials who disapproved of Guevara's pro- Chinese communist stance on the Sino-Soviet split, and to serious differences between Guevara and the pragmatic Castro regarding Cuba's economic development and ideological line. Pressed by international speculation regarding Guevara's fate, Castro stated on 16 June 1965, that the people would be informed when Guevara himself wished to let them know. Still, rumors spread both inside and outside Cuba concerning the missing Guevara's whereabouts.

There are various rumors from retired Cuban officials who were around the Castro brothers that the Castro brothers and Guevara had a strong disagreement after Guevara's Algiers speech. Intelligence files from the East German embassy in Cuba detail various heated exchanges between Fidel Castro and Che Guevara after Guevara's return from Africa. Whether Castro disagreed with Guevara's criticisms of the Soviet Union or just found them unproductive to express on the world stage remains unclear.

On 3 October 1965, Castro publicly revealed an undated letter purportedly written to him by Guevara around seven months earlier which was later titled Che Guevara's "farewell letter". In the letter, Guevara reaffirmed his enduring solidarity with the Cuban Revolution but declared his intention to leave Cuba to fight for the revolutionary cause abroad. Additionally, he resigned from all his positions in the Cuban government and communist party, and renounced his honorary Cuban citizenship.