Written May 3 (April 20), 1917.

"The imperialist war is crushing the people and threatens to crush them completely. The petty-bourgeois democrats can perhaps stave off disaster for a while. But it is only the revolutionary proletariat that can prevent a tragic end."

To commemorate the anniversary of Rosa Luxemburg's murder in 1919, we republish the following introduction to a 2014 Mexican edition of her important work, Reform or Revolution. The legacy of this martyr for proletarian revolution endures through her ideas.