"His judgment of men was profound. He early saw through the flamboyance and exhibitionism of Trotsky, who fooled the world, and especially America. The whole ill-bred and insulting attitude of Liberals in the U.S. today began with our naive acceptance of Trotsky’s magnificent lying propaganda, which he carried around the world. Against it, Stalin stood like a rock and moved neither right nor left, as he continued to advance toward a real socialism instead of the sham Trotsky offered."

— W. E. B. Du Bois, On Stalin

“Trotsky has never yet held a firm opinion on any important question of Marxism. He always contrives to worm his way into the cracks of any given difference of opinion, and desert one side for the other.”

— VI Lenin, The Right of Nations to Self-Determination, Collected Works

“Trotsky is very fond of using with the learned air of the expert pompous and high-sounding phrases to explain historical phenomena in a way that is flattering to Trotsky.”

— VI Lenin, Disruption of Unity Under Cover of Outcries for Unity, Collected Works

1. The problem of Trotskyism is not a struggle between tendencies within the Chinese Communist Party, for between communists and Trotskyists there is no link, absolutely not one link: It is a question that concerns the entire people: the struggle against the Fatherland.
2. The Japanese fascists and foreigners now it. That’s why they seek to create divisions to deceive public opinion and damage the reputation of the Communists, making people believe that Communists and Trotskyists are in the same camp.
3. The Chinese Trotskyists (like the Trotskyists of other countries) do not represent a political group, much less a political party. They are nothing but a band of evil-doers, the running dogs of Japanese fascism (and of international fascism).
4. In all countries, the Trotskyists give themselves fine names in order to mask their dirty work and banditry. For example: in Spain they call themselves the United Marxist Workers Party (POUM). Do you know that it’s they who constitute the nests of spies in Madrid in Barcelona and in other places in the service of Franco?
   (...)
5. The Trotskyists are not only the enemies of Communism, they are also the enemies of democracy and of progress. They are the most infamous traitors and spies.

— Ho Chi Minh, Three letters from Ho Chi Minh

“I think that the fundamental stuff that Trotsky was based upon was erroneous and that his ulterior behaviour was wrong and his last years were even dark. The Trotskyites have not contributed anything whatsoever to the revolutionary movement; where they did most was in Peru, but they finally failed there because their methods are bad.”

— Che Guevara quoted in “Comments on ‘Critical Notes on Political Economy’

“In Cuba there is nothing published, if one excludes the Soviet bricks, which bring the inconvenience that they do not let you think; the party did it for you and you should digest it. It would be necessary to publish the complete works of Marx, Engels, Lenin, Stalin [underlined by Che in the original] and other great Marxists. Here would come to the great revisionists (if you want you can add here Khrushchev), well analyzed, more profoundly than any others and also your friend Trotsky, who existed and apparently wrote something.”

— Che Guevara, Letter to Armando Hart Dávalos