Keep this in mind the next time you watch a WWII film.

Most of the early resistance came from the left: in particular Socialist and Communist groups.

In Germany,  Gestapo records reveal that approximately 800,000 Germans in a population of more than 66 million were jailed for active resistance during the Reich's 12-year reign. Indeed, the first concentration camps, notably Dachau, built near Munich in 1933, were meant for left-wing dissidents. In 1936, a typical year, 11,687 Germans were arrested for illegal socialist activity,

For your honor and conscience! Against Bolshevism the Waffen SS calls you.

according to Peter Hoffmann's standard 1977 study, ''The History of the German Resistance, 1933-1945.''

A. J. P. Taylor, the respected British historian,  declared in the 1960's that German resistance to the Nazis was a myth, his was a widely held view. Even today many people in Germany and elsewhere believe there was little internal opposition to Hitler.  Archives from Eastern European state security agencies which have been disproving this belief.

France during occupation was in the words of Charles Maurras, the theorist of reactionary France, the 'triumph of the true France' over Socialists, Communists, Jews, Freemasons and all parliamentary, democratic traditions which were roundly accused not just of precipitating defeat but of leading France to decadence and catastrophe.

Initially almost all Resistance was urban-based: it was there that the German presence was strongest; it was there that printing facilities were available for tracts and newspapers, and it was there that the traditions of working-class solidarity, revolutionary politics, and the educational liberalisms of lycees and universities were most pronounced. 

The movement was originally driven by an ideological opposition to Nazism and Fascism, which brought individual Communists, Socialists and left-wing Catholics and Protestants into the ranks of the 'dissidents', as Resisters were initially known. They all felt they had to do something, however small or impractical, to mark their opposition to the inertia of Petainism which advised the French to return to their private lives and leave the big decisions to Petain and Laval.

The cold war left out the role of the Socialists and Communists in the fight against Fascism, but recent scholarship is beginning to put it back in its rightful place in the study of World War II resistance movements.

At Last, Recognition and Praise for the Resistance in Nazi Germany - New York Times
The Resistance in France | History Today