If the war was fought out to the end without internal disturbances a state of exhaustion would supervene such as Europe has not experienced for two hundred years. American industry would then conquer all along the line and would force us all up against the alternatives: either retrogression to nothing but agriculture for home consumption (American corn forbids anything else) or -- social transformation. I imagine, therefore, that the plan is not to push things to extremities, to more than a sham war. But once the first shot is fired, control ceases, the horse can take the bit between its teeth.
Letters: Marx-Engels Correspondence 1888