Began publishing books on ideology and "historical materialism" in the 1840s.
Source: "Introduction to Marxism."
Leon Trotsky, Vladimir Lenin, and Lev Kamenev (from left) at the second Communist Party Congress (1919).
Source: NYPL Digital Gallery
Leon Trotsky
Source: University of Texas Portrait Gallery
Joseph Stalin
Source: Wikipedia
June 1936 strike.
Source: MSN Encarta.
Léon Blum (1872-1950)
Président du Conseil (premier), 4 June 1936 to 21 June 1937 and 13 March to 8 April 1938.
Popular Front politicians in 1936.
From left: Mme. Blum, Léon Blum (SFIO [Section Française de l'Internationale Ouvrière--French Section of the Workers' International, Socialist Party]), Maurice Thorez (PCF [Parti Communiste Français--French Communist Party), Roger Salengro (SFIO, minister of the Interior). In the second row, behind Blum and Thorez, (rolling a cigarette) is Edouard Dalladier (Parti Radical [Radical Party--liberal]), defense minister.
Sources: users.dickinson.edu/~laurent/french365d/images/left_05.html and Wikipedia.
Source: La Cucaracha: The Spanish Civil War.
Nazi's invade France, occupy Paris by 1940.
"Hitler tours Paris with architect Albert Speer (left) and sculptor Arno Breker (right), 23 June 1940."
Source: Wikipedia.
For more info, see "Time Line - Europe - March 1938-May 1941" (pdf format)