Entrism is a tactical technique in which a political organization encourages its members to join another, usually large, organization in order to spread its influence, ideas and program.
Entrism was actively used by the Trotskyists , who penetrated the already existing mass organizations of the working class — the reformist Social Democratic and Communist (Stalinist) parties, as well as the trade unions associated with them — for their gradual radicalization . Leon Trotsky approved the idea of ​​Trotskyists joining the French section of the Workers' International (SFIO) - the so-called "French Turn" - in June 1934, foreseeing significant prospects for revolutionary socialist agitation in a "united front". This tactic was followed by Trotskyist organizations in the Netherlands, Belgium, Switzerland, and Poland.
In some places, the Trotskyist entrist groups have gained some influence (for example, within the Socialist Party of America and the Labor Party , especially in its youth wing and the city council of Liverpool). Such figures of the Fourth International as Michel Pablo and Jerry Healy , after the Second World War, began to defend long-term (“deep”) entrism. However, after the Militant, the British section of the Committee for the Working International , was defeated and excluded from the ranks of the Labor Party in the 1980s, the minority of Trotskyist groups (primarily the International Marxist trend ) followed the entristist trend .