He was exiled to Mexico, where he was implicated in assassination attempts of Cuban communist Julio Mella and Russian revolutionary Leon Trotsky.
Later Vidali was active in other locations, finally leading the new communist party in the Free Territory of Trieste beginning in 1947 after World War II.
In early December 1928, Mella was expelled from the Mexican Communist Party for his association with Trotskyists, but he was readmitted two weeks later.
[citation needed] Officially, José Agustín López (said to have no particular political affiliations) was charged with Mella's murder; two other known criminals, Jose Magriñat and Antonio Sanabria, were also suspects.
He led efforts to prepare, supervise and coordinate the Antifascist Worker and Peasant Militias[5] (MAOC), organized by the Spanish Communist Party since 1934.
Because he had performed military training in the Soviet Frunze Academy, Vidali, and other comrades such as Enrique Líster, are credited with markedly improving the preparation of the militias.
[7][page needed] In the 1937 pro-Republican propaganda film The Spanish Earth, Vidali was shown addressing an assembly of military personnel.
Iosif Grigulevich, a Soviet NKVD operative, and Mexican painter David Alfaro Siqueiros were also involved in the assault.
Vidali is also thought to have been closely involved with the successful infiltration of fellow NKVD operative Ramón Mercader into Trotsky's inner circle.
Reportedly Tina Modotti said to Valentín González in Spain, after he had decided not to kill Vidali, words to the effect: "You should have shot him, I hate him".
[10] The exploits of Vidali in carrying out Trotsky's assassination, and lethal purges of agents in the Soviet Union and Fulgencio Batista's Cuba (such as Sandalio Junco in the latter) [11]) gained him attention.
Julián Gorkin likened Vidali's activities, including known travels through Cuba before and after Fidel Castro's coming to power, and his presence in Turkey, Mexico, and Spain in relation to Soviet Communist activities to the far-flung exploits of British writer Ian Fleming's well-known MI-6 character in his James Bond series of novels.