INTRODUCTION
Marx and Engels were not only the theoreticians but, in the first place, they were the leaders of the proletarian revolution. It is in the study of the conditions of the proletarian struggle and its victory that they perfected the science of Marxism, the science of the proletarian revolution.
In the First International these men saw an instrument of proletarian struggle and leadership. Thru their theoretical works they supplied a guide to this leadership. Both Marx and Engels equipped themselves in the most painstaking fashion with a thorough knowledge of the conditions in the various countries so that they might give authoritative advice and instruction to the leaders of the working class movement all over Europe. Even in their old age, they set themselves to master new languages to enable them to draw from the literature and journals of the respective countries a knowledge of their various conditions. And so we find displayed in their advice and instruction to their followers an intimate knowledge of the subjective and objective conditions of the labor movement, a knowledge that would surprise any native student.
The body of this little booklet is made up of excerpts from letters written by Marx and Engels on conditions in the United States. To a large extent these conditions still prevail, at least in so far as they deal with the subjective factors of the proletarian revolution. The ideology prevailing among